Dimitris G . Papanikas | University of Patras (original) (raw)

Papers by Dimitris G . Papanikas

This paper presents a combined methodology consisting of rotor aerodynamic and aeroacoustic compu... more This paper presents a combined methodology consisting of rotor aerodynamic and aeroacoustic computation modules. Aerodynamic calculations utilise the Vortex Element Method for the description of free vortex wake, which determines the rotor flowfield. The mathematical model discretizes the wake into vortex elements. The induced velocity is calculated for the distorted wake geometry, by means of the Biot-Savart law, integrated in closed form over each of these elements. Bound circulation variations and unsteady blade airloading are computed as a result of the nonuniform induced downwash. Wake roll up process, vortex core modelling, vorticity dissipation, blade section boundary layer growth are incorporated in numerical modelling of aerodynamic computations. Computed blade loading variations are used as the basis of loading noise predictions. Aeroacoustic analysis concentrates on helicopter rotor noise prediction in time domain. The formulation is based on the Ffowcs-Williams and Hawki...

Separation Science and Technology, 1997

The analytical solution for spiral-wound module performance is a useful tool for developing expli... more The analytical solution for spiral-wound module performance is a useful tool for developing explicit equations for the local values of variables like effective pressure, water flux, salt wall concentration, and velocities for seawater feed solutions. Depending on the operating conditions, knowledge of the local values of these variables could be useful to predict possible areas on the membrane surface where

Fluid Mechanics and Its Applications, 1992

This paper describes the computational system ETNA which performs steady and unsteady flow analys... more This paper describes the computational system ETNA which performs steady and unsteady flow analysis and design of transmission and distribution pipe networks. The system simulates the significant elements of a network, carries out conceptual design and uses optimization procedures with respect to installation and operational cost. Additionally the system carries out engineering calculations such as design of thermal insulation and performs standardization according to international standards.

Journal of Battlefield Technology, 2008

This study investigates the effect of the aerodynamic jump phenomenon on the flat-fire free fligh... more This study investigates the effect of the aerodynamic jump phenomenon on the flat-fire free flight trajectory motion of projectiles launched horizontally at various angles from low-speed helicopters. The ammunition used was the 30-mm-diameter XM788 projectile type fired from M230 machine automatic cannon. Modified linear 6-DOF flight simulation modelling was applied to the free-trajectory prediction of spin-stabilized projectiles. This analysis includes variable coefficients of the most significant aerodynamic forces, moments, and Magnus effects, which have been taken from official tabulated database, in addition to gravity acceleration. During the entire atmospheric flight the coupled epicyclic pitching and yawing motion analysis is taken into account.

International Journal of Business Innovation and Research, 2015

The maritime domain; a sub domain of the wider critical infrastructure domain plays a decisive ro... more The maritime domain; a sub domain of the wider critical infrastructure domain plays a decisive role in the worldwide digital economy and collaborative environments where leading information and communication technology is being utilised. In addition, the emerging technology of cloud computing is providing holistic frameworks for generating and delivering a plethora of interoperable, cost effective and scalable e-services creating new business opportunities and immediate profit when implemented. Driven by this motivation, a perspective beyond the traditional information and communication systems' utilisation; a road-map to maritime cloud is proposed. The digital frontiers of the 'Cyber Ocean' and the strategic approach for the creation of the maritime cloud environment are defined and the maritime cloud architecture is designed in order to host innovative maritime services in a new era of technology for the maritime domain.

14th AIAA/AHI Space Planes and Hypersonic Systems and Technologies Conference, 2006

An analytical method is created for the calculation of the aerodynamic characteristics of Space V... more An analytical method is created for the calculation of the aerodynamic characteristics of Space Vehicles during their flight in hypersonic regime. The simplicity of this method lies on the fact that it only needs the Spacecraft's geometry in conjunction with a small number of experimental (wind tunnel) data. The analysis is based on the Newtonian Flow theory. Several basic assumptions are taken into account. The flow is considered inviscid, the pressure coefficient after the shockwave remains constant, the upper surface pressure coefficient is equal to zero and the lower surface pressure coefficient is given as a function of the Spacecraft's angle of attack. The Space Vehicle is modeled as a flat plate with constant unit-length wing span. The lift and drag coefficients during hypersonic flight can be calculated from the normal force coefficient and the Spacecraft's angle of attack. The lower surface of these Space Vehicles is considered be flat. Their dihedral angle is small. The wing's top view is modeled with straight lines between known and predetermined points on the Spacecraft. Taking into account the fact that the Space Vehicle's hypersonic aerodynamic attitude is similar to that of a flat plate, and it has finite and non-constant wing span which is modeled with straight lines as mentioned above, the Newtonian Flow theory is being developed for every Spacecraft separately. In the current analysis the Finite Wing Span Newtonian Flow (FWSNF) models for two specific Spacecrafts, the STS Shuttle Orbiter and the X-34 vehicle, are being developed in details.

International Journal of Electronic Security and Digital Forensics, 2012

ABSTRACT Although small, medium and micro enterprises (SMEs, mEs) play a decisive role in the Eur... more ABSTRACT Although small, medium and micro enterprises (SMEs, mEs) play a decisive role in the European digital economy, they have been identified as one of the weakest links in information security. Identifying these security weaknesses and needs, we parameterise our open collaborative environment STORM in order to offer trusted services for SMEs/mEs to self-manage the security of their information and telecommunication (IT) systems.

IEEE Security & Privacy, 2015

ABSTRACT The automotive industry has used emerging technological concepts to transform automobile... more ABSTRACT The automotive industry has used emerging technological concepts to transform automobiles into sophisticated cyber platforms. However, this extended technological evolution hides multiple security risks capable of affecting both the intelligent transportation domain and human life itself.

Renewable Energy, 2007

The paper demonstrates a computational methodology for the noise prediction of an horizontal axis... more The paper demonstrates a computational methodology for the noise prediction of an horizontal axis wind turbine (HAWT) rotor in time domain. The aeroacoustic modeling is based on the Ffowcs Williams and Hawkings equation considering only the surface monopole and dipole ...

Journal of Fluids Engineering, 1997

The object of the present study is to access the performance of an airlift pump under predetermin... more The object of the present study is to access the performance of an airlift pump under predetermined operating conditions. The gas-liquid-solid three phase flow in an airlift pump is described by a system of differential equations, which derives from the fundamental conservation equations of continuity and momentum. This approach leads to a more general mathematical model which is applicable to a wide range of installations, from small airlift pumps to very large systems, suitable for deep-sea mining. For the frictional pressure drop calculation a new correlation, based on a pseudoliquid model, has been proposed. In addition, parameters such as the drag coefficient of both solid and gas phase, the shape of particles and the compressibility factor, which is very important for deep-sea mining, have been incorporated in the governing equations. The application of the computational algorithm to different geometry and flow conditions of an airlift pump leads to the optimization of the sys...

This paper presents the results of a theoretical analysis of a boundary layer for a two-dimension... more This paper presents the results of a theoretical analysis of a boundary layer for a two-dimensional gas-particle flow over a flat plate. The relevant differential equations are solved by using the momentum-integral method. The analysis is carried out using particle velocity and density profiles which are functions of any polynomial gas velocity profile. Both laminar and turbulent boundary layers can therefore be examined. The boundary-layer characteristic magnitudes for particles of spherical or nonspherical shape, with different densities and diameters, are calculated by using a gneralized relationship for the drag coefficient. The results clearly show the influence of the drag coefficient on the development of the boundary layer and indicate the limit to the use of Stokes law in such problems. The analysis methods have been combined in an easily used program which is a very good tool for the theoretical diagnosis of two-dimensional gas-particle flows.

Journal of Atmospheric and Terrestrial Physics, 1979

Ahstmct-In the altitude region between 52 and 117km measurements of total density and temperature... more Ahstmct-In the altitude region between 52 and 117km measurements of total density and temperature were performed by Pitot tubes, mass spectrometers and H-Lwan-o photometers. These data were obtained during the Western European Winter Anomaly Campaign 1975/76 under highly disturbed conditions. Substantial deviations from the CIRA (1972) model are found. which indicate pronounced wavelike disturbances in the atmosphere. l. INmoDuclIoN

International Journal of Computing Science and Mathematics, 2008

Estudo da degradação da biomassa de três espécies de ...

Comptes Rendus Mécanique, 2003

Designing natural gas pipelines to safely and efficiently handle unsteady flows, requires knowled... more Designing natural gas pipelines to safely and efficiently handle unsteady flows, requires knowledge of pressure drop, flowrate and temperature distribution throughout the system. The accurate prediction of these parameters is essential in order to achieve optimum cumulative deliverability, and safe and reliable operation. An Adaptive Method of Lines algorithm is formulated for the solution of Euler system of equations, which fully simulates slow and fast transients. Two test cases present the improvement of the numerical solution from grid adaptation. Good results are obtained both for slow and fast transients simulations proving that the suggested numerical procedure is appropriate for such predictions. To cite this article: E.

NASA STI/Recon Technical …, 1975

Title: High power Arc heaters and expansion nozzles for high enthalpy flow investigations. Author... more Title: High power Arc heaters and expansion nozzles for high enthalpy flow investigations. Authors: Fiebig, M.; Kindler, K.; Papanikas, DG. ... Publication: High power Arc heaters and expansion nozzles for high enthalpy flow investigations Transl. ...

… of Engineering (IJE), 2010

In the present paper a computational investigation is made about the efficiency of recently devel... more In the present paper a computational investigation is made about the efficiency of recently developed mathematical models for specific aerodynamic phenomena of the complicated helicopter rotor flowfield. A developed computational procedure is used, ...

9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 2006

Journal of the American Helicopter Society

In a cooperative research program between eight European partners, a 40% geometrically and dynami... more In a cooperative research program between eight European partners, a 40% geometrically and dynamically scaled and highly instrumented model of the ECD (formerly MBB) BO 105 helicopter main rotor was tested in the open-jet anechoic test section of the German-Dutch Wind Tunnel (DNW) in the Netherlands. The primary objectives of this experimental study were to: (1) to improve the physical