Ángel Sanz-Andres - Academia.edu (original) (raw)

Papers by Ángel Sanz-Andres

Journal of Sound and Vibration, Jul 1, 2010

Some elastic bluff bodies under the action of a fluid flow can experience transverse galloping an... more Some elastic bluff bodies under the action of a fluid flow can experience transverse galloping and lose stability if the flow velocity exceeds a critical value. For flow velocities higher than this critical value, there is an energy transfer from the flow to the body and the body develops an oscillatory motion. Usually, it is considered as an undesirable effect for civil or marine structures but here we will show that if the vibration is substantial, it can be used to extract useful energy from the surrounding flow. This paper explores analytically the potential use of transverse galloping in order to obtain energy. To this end, transverse galloping is described by a one-degree-offreedom model where fluid forces obey the quasi-steady hypothesis. The influence of cross-section geometry and mechanical properties in the energy conversion factor is investigated.

: This chapter describes the phenomenon of heat transfer across a mechanical interface, quantifie... more : This chapter describes the phenomenon of heat transfer across a mechanical interface, quantified through the thermal contact conductance, which mainly depends on contact pressure, surface finish and mechanical properties, and the presence of interstitial materials. Main models to estimate this parameter are presented as well as experimental results obtained over the last decades, focusing on those that can be applied to thermal modelling of spacecraft. The different types of thermal fillers, materials used to improve the thermal contact conductance are presented.

Elsevier eBooks, 2012

In this chapter, the main points concerning thermal control testing are considered. Namely: the p... more In this chapter, the main points concerning thermal control testing are considered. Namely: the phases of a spacecraft project, the objectives associated with the tests performed in the different phases; the types of tests, the main characteristics of these tests, the sources of uncertainty in the tests, the project model philosophy to be considered and the hardware models involved; the test facilities where thermal tests are performed, and their coordination and the effort for standardization of production and testing activities in Europe.

Elsevier eBooks, 2012

The aim of this chapter is to explain the basic physical principle on which the phase change capa... more The aim of this chapter is to explain the basic physical principle on which the phase change capacitors are based, their applications in a thermal control subsystem, the ways they are used, the main characteristics that the phase change material should have, the relevant physical characteristics affecting these materials, and the main materials selected for space applications. Also, some basic aspects of the technology involved, such as the constituents of the phase change capacitor, bellows or metallic membranes, and materials used as thermal enhancers in powder or foam form, are included.

Journal of Wind Engineering and Industrial Aerodynamics, Oct 1, 2019

Overhead power lines are protected from electrical discharges (that occur during storms) by the s... more Overhead power lines are protected from electrical discharges (that occur during storms) by the so-called "guard cables", which are placed above the power conductors. In some places, they are provided with beacon spheres. A new instability in these cables, under a longitudinal wind, has recently been reported. The motion of the cable can damage their supports, and causing interference with the power lines, leading to cable breakage, and reducing energy availability supplied by the transmission line. The reported instabilities include oscillation and autorotation motions. In previous papers, the vortex-induced vibration has been suggested as the mechanism that can explain the system oscillations at low speed, and presented the lateral quasi-steady aerodynamic force that can justify both the autorotation motion of a sphere and the oscillations at large speed. In this paper, results of wind tunnel tests concerning a simplified system, a single sphere in a swing configuration, are reported, considering the influence of the main parameters involved: cable span and sag, beacon mass, surface roughness, and reduced wind speed. The limits of the regions corresponding to different motion behaviours (oscillation, autorotation, transitions) are presented in the wind velocity-sag map. Autorotation results have been compared with available theoretical models.

Acta Astronautica, Jun 1, 2022

Journal of Wind Engineering and Industrial Aerodynamics, Aug 1, 2009

Advances in Space Research, 2003

UPM-Sat 1 is a small scientific, in-orbit demonstration, educational satellite which has been des... more UPM-Sat 1 is a small scientific, in-orbit demonstration, educational satellite which has been designed, built, tested, integrated, launched and operated by a team of professors, students, and auxiliary personnel belonging to the Universidad Politecnica de Madrid (UPM). After completion of UPM-Sat 1 Mission a new small satellite, UPM-Sat 2, oriented to low-Earth-orbit scientific mission has been designed. In this paper the different subsystems of UPM-Sat 1 are described and the main characteristics of the second small satellite UPM-Sat 2 are outlined.

Acta Astronautica, May 1, 2020

Long Duration Balloon missions are key platforms for scientific research and space technology dev... more Long Duration Balloon missions are key platforms for scientific research and space technology development. Thermal analyses of this kind of systems are crucial for the success of the mission. Even though the science is usually performed at float altitude, the ascent phase, usually non-operational, is where the extreme cold conditions occur, due to the convective effects caused by relative wind speed together with the low temperatures found in the tropopause, making this scenario a dimensioning case. In this paper, a thorough study of the thermal environmental conditions during the ascent is carried out, in particular winds, temperature, and radiative thermal loads have been obtained as a function of the altitude. The study is based on real data obtained from different sources, including atmospheric soundings, radar and satellite, and a meticulous statistical treatment. The study is focussed on one of the main stratospheric balloon launch sites in Europe, Esrange (Sweden), a center of the Swedish Space Corporation, and the analyses are performed for the summer period. However, the methodology can be extended to any other location and epoch. As an example, the convective effect of the horizontal winds on a plate has been studied, and the heat transfer during the ascent phase has been quantified. A subcooling of around 7°C was found in this case, which make worth the dedicated analysis.

The Scientific World Journal, 2015

A new, simple, and quick-calculation methodology to obtain a solar panel model, based on the manu... more A new, simple, and quick-calculation methodology to obtain a solar panel model, based on the manufacturers' datasheet, to perform MPPT simulations, is described. The method takes into account variations on the ambient conditions (sun irradiation and solar cells temperature) and allows fast MPPT methods comparison or their performance prediction when applied to a particular solar panel. The feasibility of the described methodology is checked with four different MPPT methods applied to a commercial solar panel, within a day, and under realistic ambient conditions.

Acta Astronautica, Jul 1, 2018

The selection of the extreme thermal environmental conditions-albedo coefficient and Earth infrar... more The selection of the extreme thermal environmental conditions-albedo coefficient and Earth infrared radiationfor the thermal design of stratospheric balloon missions is usually based on the methodologies applied in space missions. However, the particularities of stratospheric balloon missions, such as the much higher residence time of the balloon payload over a determined area, make necessary an approach centered in the actual environment the balloon is going to find, in terms of geographic area and season of flight. In this sense, this work is focussed on stratospheric balloon missions circumnavigating the North Pole during the summer period. Pairs of albedo and Earth infrared radiation satellite data restricted to this area and season of interest have been treated statistically. Furthermore, the environmental conditions leading to the extreme temperatures of the payload depend in turn on the surface finish, and more particularly on the ratio between the solar absorptance and the infrared emissivity α/ε. A simple but representative thermal model of a balloon and its payload has been set up in order to identify the pairs of albedo coefficient and Earth infrared radiation leading to extreme temperatures for each value of α/ε.

Journal of Wind Engineering and Industrial Aerodynamics, Aug 1, 2005

Different methods to reduce the high suction caused by conical vortices have been reported in the... more Different methods to reduce the high suction caused by conical vortices have been reported in the literature: vertical parapets, either solid or porous, placed at the roof edges being the most analysed configuration. Another method for alleviating the high suction peaks due to conical vortices is the use of some non-standard parapet configuration like cantilever parapets. In this paper the influence of roof curvature on the conical vortex pattern appearing on a curved roof (Fig. 1) when subject to oblique winds is experimentally analysed by testing the mean pressure distribution on the curved roofs of low-rise building models in a wind tunnel. Also, the efficiency of cantilever parapets to reduce mean suction loads on curved roofs is experimentally checked. Very high suction loads have been measured on curved roofs, the magnitude of these high suction loads being significantly decreased when cantilever parapets are used. Thus, the suitability of these parapets to reduce wind pressure loads on curved roofs is demonstrated.

Journal of physics, Nov 1, 2021

In the present work, the effect of the friction forces at bearings on cup anemometer performance ... more In the present work, the effect of the friction forces at bearings on cup anemometer performance is studied. The study is based on the classical analytical approach to cup anemometer performance (2-cup model), used in the analysis by Schrenk (1929) and Wyngaard (1981). The friction torque dependence on temperature was modelled using exponential functions fitted to the experimental results from RISØ report #1348 by Pedersen (2003). Results indicate a logical poorer performance (in terms of a lower rotation speed at the same wind velocity), with an increase of the friction. However, this decrease of the performance is affected by the aerodynamic characteristics of the cups. More precisely, results indicate that the effect of the friction is modified depending on the ratio between the maximum value of the aerodynamic drag coefficient (at 0° yaw angle) and the minimum one (at 180° yaw angle). This reveals as a possible way to increase the efficiency of the cup anemometer rotors. Besides, if the friction torque is included in the equations, a noticeable deviation of the rotation rate (0.5-1% with regard to the expected rotation rate without considering friction) is found for low temperatures.

Elsevier eBooks, 2012

This chapter outlines the design objectives and the requirements of the spacecraft components for... more This chapter outlines the design objectives and the requirements of the spacecraft components for the different modes of operation, and the tasks to be considered in the design process: the selection of the thermal hardware and the prediction of the temperatures in the spacecraft selected points. The main design philosophy and the flow of the design process are highlighted, the definition of the worst load cases (hot cases, cold cases) and the temperature design margins are presented, and their roles in the design are explained.

Journal of Wind Engineering and Industrial Aerodynamics, Aug 1, 2002

A simple analytical model for the train-induced flow and its effects on pedestrians is presented ... more A simple analytical model for the train-induced flow and its effects on pedestrians is presented in this paper. The expressions developed for the induced air velocity and pressure on the pedestrian surface, as well as their dependence with time, are obtained from unsteady potential theory. The relevant parameters and their effects are analysed, in particular the sensitivity of the pressure coefficient and its rate of change on the train and pedestrian transverse size, the distance to the tracks and the pressure measurement location on the pedestrian surface. In spite of the extreme simplicity of the model and the expressions obtained, good correlation is observed with previously existing experiments. With this work, an absence of published studies concerning analytical approaches to the problem of vehicleinduced pressure on pedestrians is intended to be covered, allowing for simplified testing procedures.

Sensors, Dec 13, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

: The basic concepts concerning spacecraft trajectory, or orbit, are described. The orbit transfe... more : The basic concepts concerning spacecraft trajectory, or orbit, are described. The orbit transfers (co-planar or Hohmann, and orbit plane inclination change), the orbit in space, and the main orbit perturbations (non-gravitational forces, non-spherical mass distributions, interactions with third bodies) are also considered, as well as lighting conditions for spacecraft (eclipse, occultation, umbra) and the types of orbits, their relation with the mission, and their impact on the spacecraft subsystem design.

: This chapter deals with cryogenic systems, which, from the point of view of spacecraft thermal ... more : This chapter deals with cryogenic systems, which, from the point of view of spacecraft thermal control, are those concerned with operating temperatures below 100 K. Leaving aside radiators ( Chapter 8) cryogenic systems can be classified as open cycle refrigerators (which use stored cryogens, either solid or liquid), and closed cycle refrigerators (including regenerative and recuperative systems).

Journal of Sound and Vibration, Jul 1, 2010

Some elastic bluff bodies under the action of a fluid flow can experience transverse galloping an... more Some elastic bluff bodies under the action of a fluid flow can experience transverse galloping and lose stability if the flow velocity exceeds a critical value. For flow velocities higher than this critical value, there is an energy transfer from the flow to the body and the body develops an oscillatory motion. Usually, it is considered as an undesirable effect for civil or marine structures but here we will show that if the vibration is substantial, it can be used to extract useful energy from the surrounding flow. This paper explores analytically the potential use of transverse galloping in order to obtain energy. To this end, transverse galloping is described by a one-degree-offreedom model where fluid forces obey the quasi-steady hypothesis. The influence of cross-section geometry and mechanical properties in the energy conversion factor is investigated.

: This chapter describes the phenomenon of heat transfer across a mechanical interface, quantifie... more : This chapter describes the phenomenon of heat transfer across a mechanical interface, quantified through the thermal contact conductance, which mainly depends on contact pressure, surface finish and mechanical properties, and the presence of interstitial materials. Main models to estimate this parameter are presented as well as experimental results obtained over the last decades, focusing on those that can be applied to thermal modelling of spacecraft. The different types of thermal fillers, materials used to improve the thermal contact conductance are presented.

Elsevier eBooks, 2012

In this chapter, the main points concerning thermal control testing are considered. Namely: the p... more In this chapter, the main points concerning thermal control testing are considered. Namely: the phases of a spacecraft project, the objectives associated with the tests performed in the different phases; the types of tests, the main characteristics of these tests, the sources of uncertainty in the tests, the project model philosophy to be considered and the hardware models involved; the test facilities where thermal tests are performed, and their coordination and the effort for standardization of production and testing activities in Europe.

Elsevier eBooks, 2012

The aim of this chapter is to explain the basic physical principle on which the phase change capa... more The aim of this chapter is to explain the basic physical principle on which the phase change capacitors are based, their applications in a thermal control subsystem, the ways they are used, the main characteristics that the phase change material should have, the relevant physical characteristics affecting these materials, and the main materials selected for space applications. Also, some basic aspects of the technology involved, such as the constituents of the phase change capacitor, bellows or metallic membranes, and materials used as thermal enhancers in powder or foam form, are included.

Journal of Wind Engineering and Industrial Aerodynamics, Oct 1, 2019

Overhead power lines are protected from electrical discharges (that occur during storms) by the s... more Overhead power lines are protected from electrical discharges (that occur during storms) by the so-called "guard cables", which are placed above the power conductors. In some places, they are provided with beacon spheres. A new instability in these cables, under a longitudinal wind, has recently been reported. The motion of the cable can damage their supports, and causing interference with the power lines, leading to cable breakage, and reducing energy availability supplied by the transmission line. The reported instabilities include oscillation and autorotation motions. In previous papers, the vortex-induced vibration has been suggested as the mechanism that can explain the system oscillations at low speed, and presented the lateral quasi-steady aerodynamic force that can justify both the autorotation motion of a sphere and the oscillations at large speed. In this paper, results of wind tunnel tests concerning a simplified system, a single sphere in a swing configuration, are reported, considering the influence of the main parameters involved: cable span and sag, beacon mass, surface roughness, and reduced wind speed. The limits of the regions corresponding to different motion behaviours (oscillation, autorotation, transitions) are presented in the wind velocity-sag map. Autorotation results have been compared with available theoretical models.

Acta Astronautica, Jun 1, 2022

Journal of Wind Engineering and Industrial Aerodynamics, Aug 1, 2009

Advances in Space Research, 2003

UPM-Sat 1 is a small scientific, in-orbit demonstration, educational satellite which has been des... more UPM-Sat 1 is a small scientific, in-orbit demonstration, educational satellite which has been designed, built, tested, integrated, launched and operated by a team of professors, students, and auxiliary personnel belonging to the Universidad Politecnica de Madrid (UPM). After completion of UPM-Sat 1 Mission a new small satellite, UPM-Sat 2, oriented to low-Earth-orbit scientific mission has been designed. In this paper the different subsystems of UPM-Sat 1 are described and the main characteristics of the second small satellite UPM-Sat 2 are outlined.

Acta Astronautica, May 1, 2020

Long Duration Balloon missions are key platforms for scientific research and space technology dev... more Long Duration Balloon missions are key platforms for scientific research and space technology development. Thermal analyses of this kind of systems are crucial for the success of the mission. Even though the science is usually performed at float altitude, the ascent phase, usually non-operational, is where the extreme cold conditions occur, due to the convective effects caused by relative wind speed together with the low temperatures found in the tropopause, making this scenario a dimensioning case. In this paper, a thorough study of the thermal environmental conditions during the ascent is carried out, in particular winds, temperature, and radiative thermal loads have been obtained as a function of the altitude. The study is based on real data obtained from different sources, including atmospheric soundings, radar and satellite, and a meticulous statistical treatment. The study is focussed on one of the main stratospheric balloon launch sites in Europe, Esrange (Sweden), a center of the Swedish Space Corporation, and the analyses are performed for the summer period. However, the methodology can be extended to any other location and epoch. As an example, the convective effect of the horizontal winds on a plate has been studied, and the heat transfer during the ascent phase has been quantified. A subcooling of around 7°C was found in this case, which make worth the dedicated analysis.

The Scientific World Journal, 2015

A new, simple, and quick-calculation methodology to obtain a solar panel model, based on the manu... more A new, simple, and quick-calculation methodology to obtain a solar panel model, based on the manufacturers' datasheet, to perform MPPT simulations, is described. The method takes into account variations on the ambient conditions (sun irradiation and solar cells temperature) and allows fast MPPT methods comparison or their performance prediction when applied to a particular solar panel. The feasibility of the described methodology is checked with four different MPPT methods applied to a commercial solar panel, within a day, and under realistic ambient conditions.

Acta Astronautica, Jul 1, 2018

The selection of the extreme thermal environmental conditions-albedo coefficient and Earth infrar... more The selection of the extreme thermal environmental conditions-albedo coefficient and Earth infrared radiationfor the thermal design of stratospheric balloon missions is usually based on the methodologies applied in space missions. However, the particularities of stratospheric balloon missions, such as the much higher residence time of the balloon payload over a determined area, make necessary an approach centered in the actual environment the balloon is going to find, in terms of geographic area and season of flight. In this sense, this work is focussed on stratospheric balloon missions circumnavigating the North Pole during the summer period. Pairs of albedo and Earth infrared radiation satellite data restricted to this area and season of interest have been treated statistically. Furthermore, the environmental conditions leading to the extreme temperatures of the payload depend in turn on the surface finish, and more particularly on the ratio between the solar absorptance and the infrared emissivity α/ε. A simple but representative thermal model of a balloon and its payload has been set up in order to identify the pairs of albedo coefficient and Earth infrared radiation leading to extreme temperatures for each value of α/ε.

Journal of Wind Engineering and Industrial Aerodynamics, Aug 1, 2005

Different methods to reduce the high suction caused by conical vortices have been reported in the... more Different methods to reduce the high suction caused by conical vortices have been reported in the literature: vertical parapets, either solid or porous, placed at the roof edges being the most analysed configuration. Another method for alleviating the high suction peaks due to conical vortices is the use of some non-standard parapet configuration like cantilever parapets. In this paper the influence of roof curvature on the conical vortex pattern appearing on a curved roof (Fig. 1) when subject to oblique winds is experimentally analysed by testing the mean pressure distribution on the curved roofs of low-rise building models in a wind tunnel. Also, the efficiency of cantilever parapets to reduce mean suction loads on curved roofs is experimentally checked. Very high suction loads have been measured on curved roofs, the magnitude of these high suction loads being significantly decreased when cantilever parapets are used. Thus, the suitability of these parapets to reduce wind pressure loads on curved roofs is demonstrated.

Journal of physics, Nov 1, 2021

In the present work, the effect of the friction forces at bearings on cup anemometer performance ... more In the present work, the effect of the friction forces at bearings on cup anemometer performance is studied. The study is based on the classical analytical approach to cup anemometer performance (2-cup model), used in the analysis by Schrenk (1929) and Wyngaard (1981). The friction torque dependence on temperature was modelled using exponential functions fitted to the experimental results from RISØ report #1348 by Pedersen (2003). Results indicate a logical poorer performance (in terms of a lower rotation speed at the same wind velocity), with an increase of the friction. However, this decrease of the performance is affected by the aerodynamic characteristics of the cups. More precisely, results indicate that the effect of the friction is modified depending on the ratio between the maximum value of the aerodynamic drag coefficient (at 0° yaw angle) and the minimum one (at 180° yaw angle). This reveals as a possible way to increase the efficiency of the cup anemometer rotors. Besides, if the friction torque is included in the equations, a noticeable deviation of the rotation rate (0.5-1% with regard to the expected rotation rate without considering friction) is found for low temperatures.

Elsevier eBooks, 2012

This chapter outlines the design objectives and the requirements of the spacecraft components for... more This chapter outlines the design objectives and the requirements of the spacecraft components for the different modes of operation, and the tasks to be considered in the design process: the selection of the thermal hardware and the prediction of the temperatures in the spacecraft selected points. The main design philosophy and the flow of the design process are highlighted, the definition of the worst load cases (hot cases, cold cases) and the temperature design margins are presented, and their roles in the design are explained.

Journal of Wind Engineering and Industrial Aerodynamics, Aug 1, 2002

A simple analytical model for the train-induced flow and its effects on pedestrians is presented ... more A simple analytical model for the train-induced flow and its effects on pedestrians is presented in this paper. The expressions developed for the induced air velocity and pressure on the pedestrian surface, as well as their dependence with time, are obtained from unsteady potential theory. The relevant parameters and their effects are analysed, in particular the sensitivity of the pressure coefficient and its rate of change on the train and pedestrian transverse size, the distance to the tracks and the pressure measurement location on the pedestrian surface. In spite of the extreme simplicity of the model and the expressions obtained, good correlation is observed with previously existing experiments. With this work, an absence of published studies concerning analytical approaches to the problem of vehicleinduced pressure on pedestrians is intended to be covered, allowing for simplified testing procedures.

Sensors, Dec 13, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

: The basic concepts concerning spacecraft trajectory, or orbit, are described. The orbit transfe... more : The basic concepts concerning spacecraft trajectory, or orbit, are described. The orbit transfers (co-planar or Hohmann, and orbit plane inclination change), the orbit in space, and the main orbit perturbations (non-gravitational forces, non-spherical mass distributions, interactions with third bodies) are also considered, as well as lighting conditions for spacecraft (eclipse, occultation, umbra) and the types of orbits, their relation with the mission, and their impact on the spacecraft subsystem design.

: This chapter deals with cryogenic systems, which, from the point of view of spacecraft thermal ... more : This chapter deals with cryogenic systems, which, from the point of view of spacecraft thermal control, are those concerned with operating temperatures below 100 K. Leaving aside radiators ( Chapter 8) cryogenic systems can be classified as open cycle refrigerators (which use stored cryogens, either solid or liquid), and closed cycle refrigerators (including regenerative and recuperative systems).