A Real-time Method for Estimating Viscous Forebody Drag Coefficients PDF Download
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Author: Stephen A. Whitmore
Publisher:
ISBN:
Category : Drag (Aerodynamics)
Languages : en
Pages : 36
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Book Description
This paper develops a real-time method based on the law of the wake for estimating forebody skin-friction coefficients. The incompressible law-of-the-wake equations are numerically integrated across the boundary layer depth to develop an engineering model that relates longitudinally averaged skin-friction coefficients to local boundary layer thickness. Solutions applicable to smooth surfaces with pressure gradients and rough surfaces with negligible pressure gradients are presented. Model accuracy is evaluated by comparing model predictions with previously measured flight data. This integral law procedure is beneficial in that skin-friction coefficients can be indirectly evaluated in real-time using a single boundary layer height measurement. In this concept a reference pitot probe is inserted into the flow, well above the anticipated maximum thickness of the local boundary layer. Another probe is servomechanism-driven and floats within the boundary layer. A controller regulates the position of the floating probe. The measured servomechanism of this second probe provides an indirect measurement of both local and longitudinally averaged skin friction. Simulation results showing the performance of the control law for a noisy boundary layer are then presented.
Author: Stephen A. Whitmore
Publisher:
ISBN:
Category : Drag (Aerodynamics)
Languages : en
Pages : 36
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Book Description
This paper develops a real-time method based on the law of the wake for estimating forebody skin-friction coefficients. The incompressible law-of-the-wake equations are numerically integrated across the boundary layer depth to develop an engineering model that relates longitudinally averaged skin-friction coefficients to local boundary layer thickness. Solutions applicable to smooth surfaces with pressure gradients and rough surfaces with negligible pressure gradients are presented. Model accuracy is evaluated by comparing model predictions with previously measured flight data. This integral law procedure is beneficial in that skin-friction coefficients can be indirectly evaluated in real-time using a single boundary layer height measurement. In this concept a reference pitot probe is inserted into the flow, well above the anticipated maximum thickness of the local boundary layer. Another probe is servomechanism-driven and floats within the boundary layer. A controller regulates the position of the floating probe. The measured servomechanism of this second probe provides an indirect measurement of both local and longitudinally averaged skin friction. Simulation results showing the performance of the control law for a noisy boundary layer are then presented.
Author:
Publisher:
ISBN:
Category : Skin friction (Aerodynamics)
Languages : en
Pages :
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Author: Stephen A. Whitmore
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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Book Description
Author: Rose McCallen
Publisher: Springer Science & Business Media
ISBN: 354044419X
Category : Technology & Engineering
Languages : en
Pages : 534
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Book Description
It is our pleasure to present these proceedings from the United Engineering Foundation Conference on The Aerodynamics of Heavy Vehicles: Trucks, Buses and Trains held December 2-6, 2002, in Monterey, California. This Department of Energy, United Engineering Foundation, and industry sponsored conference brought together 90 leading engineering researchers from around the world to discuss the aerodynamic drag of heavy vehicles. Participants from national labs, academia, and industry, including truck manufacturers, discussed how computer simulation and experimental techniques could be used to design more fuel efficient trucks, buses, and trains. Conference topics included comparison of computational fluid dynamics calculations using both steady and unsteady Reynolds-averaged Navier-Stokes, large-eddy simulation, and hybrid turbulence models and experimental data obtained from the Department of Energy sponsored and other wind tunnel experiments. Advanced experimental techniques including three-dimensional particle image velocimetry were presented, along with their use in evaluating drag reduction devices. We would like to thank the UEF conference organizers for their dedication and quick response to sudden deadlines. In addition, we would like to thank all session chairs, the scientific advisory committee, authors, and reviewers for their many hours of dedicated effort that contributed to a successful conference and resulted in this document of the conference proceedings. We also gratefully acknowledge the support received from the United Engineering Foundation, the US Department of Energy, Lawrence Livermore National Laboratory, Volvo Trucks America, International Truck and Engine Corporation, and Freightliner LLC.
Author:
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 948
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 606
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 148
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Book Description
A digital-computer program has been written for calculating the viscous drag of streamlined bodies of revolution in constant-density axial flow. The integral approach adopted incorporates recently improved methods for predicting the transition point and for calculating the turbulent boundary layer. The inputs to the computer program are the body geometry, the associated inviscid pressure distribution, and the body-length Reynolds number. Agreement of calculated and measured drag coefficients is good, particularly in cases where the transition point is predicted accurately. (Author).
Author: R. G. S. White
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 7
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Author: R. G. Barker
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
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A method is presented for computing the aerodynamic drag of a body in free flight. Polynomial least squares smoothing of position data is used for the first estimate with an optional provision of improving these results by matching arc length. All values thus obtained from one or more drops are then used to obtain a single least squares fit with the drag coefficient formula of T.S. Walton and Daniel Shanks. The nonlinear portions of this fitting problem are solved with good results using a quadratic minimization routine provided the data cover a sufficient Mach number range. This method is both fast and accurate. It replaces a procedure which was more expensive in computer time and in the required efforts of experienced personnel. (Author).
Author:
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 616
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