Robert Robins - Academia.edu (original) (raw)
Papers by Robert Robins
Approved for public release; distribution is unlimited.
In Robins and Delisi (2008), a linear decay model, a new IGE model by Sarpkaya (2006), and a seri... more In Robins and Delisi (2008), a linear decay model, a new IGE model by Sarpkaya (2006), and a series of APA-Based models were scored using data from three airports. This report is a guide to the APA-based models.
Radiowave scintillation in the presence of natural and/or high-altitude nuclear disturbances has ... more Radiowave scintillation in the presence of natural and/or high-altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma-density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model is incorporated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction theory. The model is based on similarly extensive analysis of wideband data from two equatorial stations. It describes irregularities at an effective height of 350 km that are isotropic across the geomagnetic field and elongated by a factor of 50 along the field and whose one-dimensional spatial power spectrum obeys a single-regime power law with a (negative) spectral index of 1.5. The height-integrated spectral strength of the irregularities is modeled as a function of solar epoch (sunspot number), the angle between the sunset terminator and the geomagnetic field line through the equatorial F layer point in question (a measure of seasonal and longitudinal variation), time after E-layer sunset on that field line, and the F-layer magnetic apex latitude of the point. The report also highlights a factor missing from complete characterization of themore » joint seasonal/longitudinal variation of scintillation, thought to depend upon thermospheric neutral winds.« less
Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. ... more Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (ST1) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA's scientific and technical information.
Physics of Fluids A: Fluid Dynamics, 1991
First results are presented for a laboratory experiment and a supporting numerical simulation of ... more First results are presented for a laboratory experiment and a supporting numerical simulation of the evolution of a vortex pair in a stratified and sheared flow where the Richardson number is 1.0 and the vortex Reynolds number is 14 400. Both the laboratory experiment and the numerical model show that the vortex pair evolves into a single vortex. It is believed that these are the first reported experimental measurements on the evolution of a vortex pair in a stratified shear flow.
Journal of Aircraft, 2001
ABSTRACT
From July through September 2015, concurrent and collocated measurements of temperature profiles ... more From July through September 2015, concurrent and collocated measurements of temperature profiles from two passive radiometers and a RADARRASS (Radio Acoustic Sounding System) were made at a site near the ocean just to the west of Los Angeles International Airport (LAX). This site is managed by the South Coast Air Quality Management District (SCAQMD). Temperature profiles for the same time period from NOAA’s Rapid Refresh (RAP) hourly-updated assimilation/modeling system were included in the collection of profile data. For all temperature profiles a standard algorithm was used to convert temperature to dry potential temperature (PT). Data acquired at times when there was precipitation or fog were discarded. Humidity effects were not considered. It is important to note that all sensors were well maintained during the data acquisition period and that the ground based remote temperature profiling instruments involved were not part of data assimilation for RAP. The motivation for this da...
Notes on Numerical Fluid Mechanics (NNFM), 1996
We have computed numerical solutions to the 3-D Navier-Stokes equations for a stratified, incompr... more We have computed numerical solutions to the 3-D Navier-Stokes equations for a stratified, incompressible fluid. Our results show that stratification significantly modifies the phenomena that occur during the vertical migration and linking instability of trailing vortices. In particular we show that stratification accelerates the development of the linking instability and suppresses the vertical migration of the trailing vortices.
This Phase I SBIR project addressed the problem of processing the All-Sky Imaging Photometer (ASI... more This Phase I SBIR project addressed the problem of processing the All-Sky Imaging Photometer (ASIP) images collected in support of ionospheric science programs at AFGL and elsewhere. Hardware and software tools are developed that efficiently transform any image of interest to suitable world coordinates, thus removing the geometric distortions introduced by the ASIP wide-angle lens. Interactive graphical tools are demonstrated for the composite display of multiple, concurrent ASIP images, in geometrically corrected form, with a variety of correlative data from other sensor systems. Such systems might include incoherent-scatter radar, the HILAT satellite, and others. Eighteen black and white photographs are presented showing examples of actual ASIP images and test patterns in both raw and geometrically corrected form. Results demonstrating the resolution requirements of the ASIP data are included. Various aspects of the geometrical transformation and image-enhancement processing are illustrated, and example composite displays with actual ASIP and HILAT data are presented. Phase I focused on determining (1) the resolution, sensitivity, and accuracy required to capture digitally the information present in the ASIP imagery and (2) the size of computational problem involved in the required image transformations. The authors conclude that a properly integrated workstation involving both analog and digital videomore » and microcomputer-based graphical components will provide a powerful and cost-effective solution to the problem posed by the ASIP data base.« less
A MID-LATITUDE SCINTILLATION MODEL(U) NORTHWEST / RESEARCH ASSOCIATES INC BELLEVUE MA R E ROBINS ... more A MID-LATITUDE SCINTILLATION MODEL(U) NORTHWEST / RESEARCH ASSOCIATES INC BELLEVUE MA R E ROBINS ET AL 31 OCT 86 MURA-86-R004 DNA-TR-86-38i DNASi-85-C-8917 UNCLASSIFIED F/G 4/1 ML * This mailer is provided to enable DNA to maintain current distribution iists for reports. We would *appreciate your providing the requested information. 0 Add the individual listed to your distribution list. 0 Delete the cited organization/individual.
Abstract : The report contains code generalizations, comparison with experiment, and far field ca... more Abstract : The report contains code generalizations, comparison with experiment, and far field calculations.
Abstract : This report describes the formulation of a numerical procedure for simulating the turb... more Abstract : This report describes the formulation of a numerical procedure for simulating the turbulent, imcompressible flow over and behind an axisymmetric, self-propelled body. The flow is treated in three parts: (i) over the body, (ii) through the propeller, and (iii) in the very near wake of the body, where axial gradients cannot be ignored. Over most of the body, the flow is easily available from the Reynold's number of the flow and the body shape, but near the body's tail, a special treatment is required. The non-radial components of the mean flow through the propeller are obtained from a computer code based on a classical blade element analysis, while the radial component is obtained analytically in terms of the non-radial components. The effect of the propeller on the aft-body boundary layer turbulence is obtained by integrating the very near wake turbulence model equations across the plane of the propeller. In the very near wake, the flow is computed from the time-averaged Navier-Stokes equations, closed with a second-order model for the turbulence correlations. This system of equations is elliptic, so conditions at all boundaries of the very near wake region are required. In order to choose a sufficiently large solution domain without sacrificing adequate resolution just behind the propeller, the equations are transformed logarithmically.
36th AIAA Aerospace Sciences Meeting and Exhibit, 1998
The algorithm described herein predicts the trajectories and circulation decay of aircraft traili... more The algorithm described herein predicts the trajectories and circulation decay of aircraft trailing vortices. We first present the methodology used by the algorithm to simulate trailing vortex behavior, including (i) the descent of the vortices through a realistic atmosphere defined by stratification, turbulence and cross wind profiles, and (ii) the interaction of the vortices with the ground. Both the increase in separation between the vortices caused by their approaching the ground and the generation of secondary vorticity due to their interaction with the ground are modeled by the algorithm. We then compare algorithm results with field data and discuss the algorithm's validity and sensitivity. We show that the algorithm performs reasonably well for vortices out of ground effect, and produces promising results for vortices in ground effect. Since it runs in less than one-tenth of a second on a state-of-theart workstation, the algorithm is suitable for use in a real-time aircraft vortex separation system.
Journal of the Atmospheric Sciences, 1992
Journal of Aircraft, 1993
Aircraft wake vortices, evolving close to the ground in a cross wind, are a potential hazard to a... more Aircraft wake vortices, evolving close to the ground in a cross wind, are a potential hazard to aircraft landing or taking off on the same or parallel runways. The objective of this work has been to study, by means of numerical simulation, the effect of aerodynamic and environmental conditions on the generation and transport of these vortices. The approach has been to use a computer code which solves the two-dimensional, timedependent, incompressible Navier-Stokes equations expressed in stream function-vorticity form, to study wake vortices in ground effect with crosswind. The code permits the specification of arbitrary atmospheric stability and wind profiles. A mixed no-slip/free-slip lower boundary condtion has been invoked to model the interaction of the vortices with the ground. Comparisons of code output with laboratory and field data have been used to validate the code. Simulation results have shown that, even after evolution times and cross-runway transport distances on the order of 3 min and 500 m, vortices generated by large aircraft close to the ground in a crosswind can carry sufficient average circulation to be a potential hazard to smaller aircraft. Additional full-scale data need to be acquired and additional numerical comparisons need to be performed to assess the significance of these new results.
AIAA Journal, 2000
ABSTRACT
Approved for public release; distribution is unlimited.
In Robins and Delisi (2008), a linear decay model, a new IGE model by Sarpkaya (2006), and a seri... more In Robins and Delisi (2008), a linear decay model, a new IGE model by Sarpkaya (2006), and a series of APA-Based models were scored using data from three airports. This report is a guide to the APA-based models.
Radiowave scintillation in the presence of natural and/or high-altitude nuclear disturbances has ... more Radiowave scintillation in the presence of natural and/or high-altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma-density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model is incorporated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction theory. The model is based on similarly extensive analysis of wideband data from two equatorial stations. It describes irregularities at an effective height of 350 km that are isotropic across the geomagnetic field and elongated by a factor of 50 along the field and whose one-dimensional spatial power spectrum obeys a single-regime power law with a (negative) spectral index of 1.5. The height-integrated spectral strength of the irregularities is modeled as a function of solar epoch (sunspot number), the angle between the sunset terminator and the geomagnetic field line through the equatorial F layer point in question (a measure of seasonal and longitudinal variation), time after E-layer sunset on that field line, and the F-layer magnetic apex latitude of the point. The report also highlights a factor missing from complete characterization of themore » joint seasonal/longitudinal variation of scintillation, thought to depend upon thermospheric neutral winds.« less
Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. ... more Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (ST1) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA's scientific and technical information.
Physics of Fluids A: Fluid Dynamics, 1991
First results are presented for a laboratory experiment and a supporting numerical simulation of ... more First results are presented for a laboratory experiment and a supporting numerical simulation of the evolution of a vortex pair in a stratified and sheared flow where the Richardson number is 1.0 and the vortex Reynolds number is 14 400. Both the laboratory experiment and the numerical model show that the vortex pair evolves into a single vortex. It is believed that these are the first reported experimental measurements on the evolution of a vortex pair in a stratified shear flow.
Journal of Aircraft, 2001
ABSTRACT
From July through September 2015, concurrent and collocated measurements of temperature profiles ... more From July through September 2015, concurrent and collocated measurements of temperature profiles from two passive radiometers and a RADARRASS (Radio Acoustic Sounding System) were made at a site near the ocean just to the west of Los Angeles International Airport (LAX). This site is managed by the South Coast Air Quality Management District (SCAQMD). Temperature profiles for the same time period from NOAA’s Rapid Refresh (RAP) hourly-updated assimilation/modeling system were included in the collection of profile data. For all temperature profiles a standard algorithm was used to convert temperature to dry potential temperature (PT). Data acquired at times when there was precipitation or fog were discarded. Humidity effects were not considered. It is important to note that all sensors were well maintained during the data acquisition period and that the ground based remote temperature profiling instruments involved were not part of data assimilation for RAP. The motivation for this da...
Notes on Numerical Fluid Mechanics (NNFM), 1996
We have computed numerical solutions to the 3-D Navier-Stokes equations for a stratified, incompr... more We have computed numerical solutions to the 3-D Navier-Stokes equations for a stratified, incompressible fluid. Our results show that stratification significantly modifies the phenomena that occur during the vertical migration and linking instability of trailing vortices. In particular we show that stratification accelerates the development of the linking instability and suppresses the vertical migration of the trailing vortices.
This Phase I SBIR project addressed the problem of processing the All-Sky Imaging Photometer (ASI... more This Phase I SBIR project addressed the problem of processing the All-Sky Imaging Photometer (ASIP) images collected in support of ionospheric science programs at AFGL and elsewhere. Hardware and software tools are developed that efficiently transform any image of interest to suitable world coordinates, thus removing the geometric distortions introduced by the ASIP wide-angle lens. Interactive graphical tools are demonstrated for the composite display of multiple, concurrent ASIP images, in geometrically corrected form, with a variety of correlative data from other sensor systems. Such systems might include incoherent-scatter radar, the HILAT satellite, and others. Eighteen black and white photographs are presented showing examples of actual ASIP images and test patterns in both raw and geometrically corrected form. Results demonstrating the resolution requirements of the ASIP data are included. Various aspects of the geometrical transformation and image-enhancement processing are illustrated, and example composite displays with actual ASIP and HILAT data are presented. Phase I focused on determining (1) the resolution, sensitivity, and accuracy required to capture digitally the information present in the ASIP imagery and (2) the size of computational problem involved in the required image transformations. The authors conclude that a properly integrated workstation involving both analog and digital videomore » and microcomputer-based graphical components will provide a powerful and cost-effective solution to the problem posed by the ASIP data base.« less
A MID-LATITUDE SCINTILLATION MODEL(U) NORTHWEST / RESEARCH ASSOCIATES INC BELLEVUE MA R E ROBINS ... more A MID-LATITUDE SCINTILLATION MODEL(U) NORTHWEST / RESEARCH ASSOCIATES INC BELLEVUE MA R E ROBINS ET AL 31 OCT 86 MURA-86-R004 DNA-TR-86-38i DNASi-85-C-8917 UNCLASSIFIED F/G 4/1 ML * This mailer is provided to enable DNA to maintain current distribution iists for reports. We would *appreciate your providing the requested information. 0 Add the individual listed to your distribution list. 0 Delete the cited organization/individual.
Abstract : The report contains code generalizations, comparison with experiment, and far field ca... more Abstract : The report contains code generalizations, comparison with experiment, and far field calculations.
Abstract : This report describes the formulation of a numerical procedure for simulating the turb... more Abstract : This report describes the formulation of a numerical procedure for simulating the turbulent, imcompressible flow over and behind an axisymmetric, self-propelled body. The flow is treated in three parts: (i) over the body, (ii) through the propeller, and (iii) in the very near wake of the body, where axial gradients cannot be ignored. Over most of the body, the flow is easily available from the Reynold's number of the flow and the body shape, but near the body's tail, a special treatment is required. The non-radial components of the mean flow through the propeller are obtained from a computer code based on a classical blade element analysis, while the radial component is obtained analytically in terms of the non-radial components. The effect of the propeller on the aft-body boundary layer turbulence is obtained by integrating the very near wake turbulence model equations across the plane of the propeller. In the very near wake, the flow is computed from the time-averaged Navier-Stokes equations, closed with a second-order model for the turbulence correlations. This system of equations is elliptic, so conditions at all boundaries of the very near wake region are required. In order to choose a sufficiently large solution domain without sacrificing adequate resolution just behind the propeller, the equations are transformed logarithmically.
36th AIAA Aerospace Sciences Meeting and Exhibit, 1998
The algorithm described herein predicts the trajectories and circulation decay of aircraft traili... more The algorithm described herein predicts the trajectories and circulation decay of aircraft trailing vortices. We first present the methodology used by the algorithm to simulate trailing vortex behavior, including (i) the descent of the vortices through a realistic atmosphere defined by stratification, turbulence and cross wind profiles, and (ii) the interaction of the vortices with the ground. Both the increase in separation between the vortices caused by their approaching the ground and the generation of secondary vorticity due to their interaction with the ground are modeled by the algorithm. We then compare algorithm results with field data and discuss the algorithm's validity and sensitivity. We show that the algorithm performs reasonably well for vortices out of ground effect, and produces promising results for vortices in ground effect. Since it runs in less than one-tenth of a second on a state-of-theart workstation, the algorithm is suitable for use in a real-time aircraft vortex separation system.
Journal of the Atmospheric Sciences, 1992
Journal of Aircraft, 1993
Aircraft wake vortices, evolving close to the ground in a cross wind, are a potential hazard to a... more Aircraft wake vortices, evolving close to the ground in a cross wind, are a potential hazard to aircraft landing or taking off on the same or parallel runways. The objective of this work has been to study, by means of numerical simulation, the effect of aerodynamic and environmental conditions on the generation and transport of these vortices. The approach has been to use a computer code which solves the two-dimensional, timedependent, incompressible Navier-Stokes equations expressed in stream function-vorticity form, to study wake vortices in ground effect with crosswind. The code permits the specification of arbitrary atmospheric stability and wind profiles. A mixed no-slip/free-slip lower boundary condtion has been invoked to model the interaction of the vortices with the ground. Comparisons of code output with laboratory and field data have been used to validate the code. Simulation results have shown that, even after evolution times and cross-runway transport distances on the order of 3 min and 500 m, vortices generated by large aircraft close to the ground in a crosswind can carry sufficient average circulation to be a potential hazard to smaller aircraft. Additional full-scale data need to be acquired and additional numerical comparisons need to be performed to assess the significance of these new results.
AIAA Journal, 2000
ABSTRACT