scholarly journals Review of an Explanation of Aerodynamic Lift by Triple Deck Theory

2021 ◽  
Author(s):  
Alois Schaffarczyk
Keyword(s):  
Boundary Layer ◽  
Computational Fluid Dynamic ◽  
Recent Article ◽  
Fluid Dynamic ◽  
Lift Coefficient ◽  
Higher Order ◽  
Boundary Layer Theory ◽  
Cfd Models ◽  
Definition Of ◽  
Aerodynamic Lift

Inspired from a recent article by Regis , earlier publised work of McLean , , and informal discussions much earlier with members of the Danish Technical University and KTH, Sweden we summarize known results for viscous correction to the lift coefficient for thin aerodynamic profiles. We thereby try to remember [d=1]theto work of on triple-deck or higher order Boundary Layer theory and compare it to simple 2D Computational Fluid Dynamic (CFD) models. As a conclusion, a clearer definition of terms like understanding and explanation applied to the phenomena of aerodynamic lift will be given.

scholarly journals An Explanation and Understanding of Aerodynamic Lift by Triple Deck Theory

2021 ◽  
Author(s):  
Alois Schaffarczyk
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Lift Coefficient ◽  
Boundary Layer Theory ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Kutta Condition ◽  
Cfd Models ◽  
Definition Of ◽  
Aerodynamic Lift

An explanation of aerodynamic lift still is under controversial discussion as can be seen, for example, in a recent published article in Scientific American [1]. In contrast to an approach via integral conservation laws we here review an approach via the classical Kutta-Condition and its relation to boundary layer theory. Thereby we summarize known results for viscous correction to the lift coefficient for thin aerodynamic profiles and try to remember the work on triple-deck or higher order Boundary Layer theory, its connection to interactive boundary layer theory, viscous/inviscid coupling as implemented to well-known engineering code Xfoil. Finally we compare its findings to simple 2D numerical solution of full Navier Stokes equations (CFD)models. As a conclusion, a clearer definition of terms like understanding and explanation applied to the phenomenon of aerodynamic lift will be given.

Application of Magnetic Resonance (MR) Imaging for the Development and Validation of Computational Fluid Dynamic (CFD) Models of the Rat Respiratory System

2006 ◽  
Vol 18 (10) ◽  
pp. 787-794 ◽  
Author(s):  
Kevin R. Minard ◽  
Daniel R. Einstein ◽  
Richard E. Jacob ◽  
Senthil Kabilan ◽  
Andrew P. Kuprat ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Respiratory System ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Cfd Models ◽  
Development And Validation

An Evolution of Hybrid Airship Vehicle (HAV) Envelope: Aerodynamics Analysis

2014 ◽  
Vol 660 ◽  
pp. 498-502
Author(s):  
Muhammad Iyas Mahzan ◽  
Sallehuddin Muhamad
Keyword(s):  
Software Design ◽  
Computational Fluid Dynamic ◽  
Aerodynamic Characteristic ◽  
Fluid Dynamic ◽  
American Institute ◽  
Request For Proposal ◽  
Final Design ◽  
Cargo Transportation ◽  
Lift And Drag ◽  
Aerodynamic Lift

HAV has a potential application as the new means to carry Ultra Heavy Payload cargo since it combines the buoyancy capabilities of Lighter-than-Air (LTA), and the aerodynamics of lifting body of Heavier-than-Air (HTA) for speed. Due to its potential, American Institute of Aeronautics and Astronautics (AIAA) has issued a Request for Proposal (RFP) regarding the Hybrid Airship Vehicle (HAV) as cargo transportation with several requirements. AIAA RFP required an envelope that can produce 60% of the lift from buoyancy and 40% of lift from aerodynamic. To satisfy the RFP requirements, this paper analyzed 4 different designs using Computational Fluid Dynamic (CFD) software. Design 4 was chosen as the final design because it meets all the requirements. It was found that at 5° Angle of Attack (AOA), the envelope produce highest aerodynamic lift over drag (L/D) ratio of 3.79. At higher AOA, flow separation occurs at the envelope tail section jeopardizing the aerodynamic characteristic of Design 4 envelope. The lift and drag force graphs were plotted at this AOA and it was found that the HAV envelope is capable of performing the tasks in the RFP.

Experimental Investigation of an Ultra-High Bypass Ratio Embedded Boundary Layer Ingesting Propulsor for Subsonic Cruise Aircraft

2020 ◽  
Author(s):  
David J. Arend ◽  
John D. Wolter ◽  
Stefanie M. Hirt ◽  
John A. Gazzaniga ◽  
William T. Cousins ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Stability Margin ◽  
Peak Time ◽  
Peak Efficiency ◽  
Speed Test ◽  
Test Conditions ◽  
Bypass Ratio

Abstract An experimental investigation has been completed of the performance and operability of a first of its kind 0.289 scale boundary layer ingesting propulsor within the new 6.5ft × 6ft transonic embedded propulsor testbed of NASA’s 8ft × 6ft Supersonic Wind Tunnel. This propulsor consisted of a coupled inlet and distortion-tolerant fan stage design embedded in a simulated upper aft hybrid wing body aircraft installation. The boundary layer ingesting inlet had a length-to-diameter ratio of 0.67. The distortion tolerant fan was 22 inches in diameter and had a stage pressure ratio of 1.34 and a bypass ratio of 16. The embedded propulsor was evaluated at its Mach 0.78 local freestream conditions. At peak efficiency 100% design speed test conditions, it provided a mass flow weighted inlet total pressure recovery of 96.5% and an adiabatic fan stage efficiency of 87.9%. These values differed meaningfully from the pre-test computational fluid dynamic analysis based design intent. At this operating condition, the effects of inlet-fan coupling extended approximately 0.45 fan diameters upstream into the inlet. The inlet was measured to have a stability margin of approximately 28% and was pre-entry boundary layer separation limited. The fan had approximately 12% of stability margin at 100% corrected speed at which conditions it was flutter limited. It exhibited otherwise flutter free operation over its entire aircraft cruise operating map. Consistently increasing levels of fan stability margin were demonstrated at successively lower fan speeds to in excess of approximately 24% at 80% corrected speed. At each of these reduced speeds, fan stability margin was full annulus stall limited. Inlet airflow distortion remained one-per-rev throughout all tested conditions. At peak efficiency 100% speed test conditions, the boundary layer ingesting inlet airflow had steady state radial and circumferential ARP1420 distortion intensities of 1.2 and 7.2%, respectively. Peak time-variant distortion intensities of 2.3% radial and 8.9% circumferential were also recorded. Comparisons to pre-test computational fluid dynamic predictions are also provided.

scholarly journals ANALYSIS OF THE USE OF SPOILER ONE LEVEL AND TWO LEVELS IN CONDITIONS OF STEADY AGAINST THE DRAG AND LIFT COEFFICIENTS ON A SEDAN TYPE CAR BY USING CFD (COMPUTATIONAL FLUID DYNAMIC)

2019 ◽  
Vol 1 (2) ◽  
pp. 58
Author(s):  
Fajar Frihdianto ◽  
Nyeyep Sri Wardani ◽  
Indah Widiastuti
Keyword(s):  
Drag Coefficient ◽  
Steady Flow ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Lift Coefficient ◽  
Color Difference ◽  
Lower Surface ◽  
Significant Difference ◽  
The Difference ◽  
Drag And Lift

<p><em>This research was simulation analyzing the condition of steady flow in around of body car made and analized computly using CFD program (Computational Fluid Dynamic). The model used was Sedan car designed with different rear end body by adding spoiler. Analyzing in this research was done by using Software 18.2–CFD Student Version. Design of the three models were compared to find out the difference in magnitude of Coefficient of Drag, Coefficient of Lift, pressure distribution, velocity distribution, and behavioral character of flow around the rear end of car in the condition of steady flow. Model was made in appropriate scale with model of Honda city 2008 sedan car</em><em>. </em><em>Observation was made to look at the behavior of fluida flows both in front and back the car in different fluid speed ranges in steady condition.</em></p><p><em>The simulation results obtained from packet CFD on each condition were; model without spoiler, model with 1 level spoiler, and model with 2 level spoiler. Where this simulation showed that CD and CL were decrease</em><em>. </em><em>One of the example was at speed 40km/hour obtained the coefficient of drag (CD) of 0.31061, 0.28603, and 0.2054, it proved that 1 level spoiler could reduce the value of drag coefficient about 7.9135% of the sedan car without spoiler, while the car with 2 level spoiler could reduce the value of drag coefficient about 33.8592% without spoiler. For the coefficient of lift (CL) on each model was -0.38487, -0.54624, and -0.62097 proved that spoiler 1 level could reduce the value of lift coeffient about 41.92845% of the sedan car without spoiler, while the car with 2 level spoiler could reduce the value of lift coefficient about 61.35984% without spoiler. On the result of pressure distrubution and relative velocity give little affect to the upper and lower surface where this was indicated by almost no color difference contours. Then, if it was indicated from streamline and the formation of vortex, there was a significant difference so that it was very influential on the size of CD and CL occoured. By changing geometric proved that the spoiler car 1 and 2 level were more aerodynamic than the car without spoiler.</em></p>

A Theoretical Investigation of the Maximum-Lift Coefficient

1935 ◽  
Vol 2 (1) ◽  
pp. A21-A27
Author(s):  
Th. von Kármán ◽  
Clark B. Millikan
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Velocity Distribution ◽  
Theoretical Investigation ◽  
Laminar Boundary Layer ◽  
Lift Coefficient ◽  
Boundary Layer Theory ◽  
First Approximation ◽  
Transition Points

Abstract In the present paper the application of a laminar boundary-layer theory, previously developed by the authors, to the problem of the maximum-lift coefficient of airfoils is discussed. The calculations are carried through in detail for a first approximation, called a single-roof profile, to the potential velocity distribution over the upper surface of an airfoil. The results indicate a large variation in Clmax with turbulence but the quantitative dependence on Reynolds’ number and turbulence is not satisfactory. The calculations are then repeated for a so-called double-roof profile which approximates to the flow over the upper surface of an N.A.C.A. 2412 airfoil. These results are compared with those obtained from an experimental investigation on the same airfoil. The agreement is considered to indicate that for moderate values of R and Clmax the phenomenon of the maximum-lift coefficient is controlled by a contest between the separation and transition points of the laminar boundary layer over the nose of the airfoil. The difficulties involved in extending the theory to larger values of R, or to airfoils whose Cl vs. α curves are not approximately linear up to the stall, are mentioned.

scholarly journals Computational Fluid Dynamic Analysis of Intracranial Aneurysmal Bleb Formation

Neurosurgery ◽  
2013 ◽  
Vol 73 (6) ◽  
pp. 1061-1069 ◽  
Author(s):  
Jeremy H. Russell ◽  
Neil Kelson ◽  
Mark Barry ◽  
Mark Pearcy ◽  
David F. Fletcher ◽  
...  
Keyword(s):  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Cerebral Aneurysms ◽  
Wall Pressure ◽  
Computational Fluid Dynamic Analysis ◽  
Unruptured Aneurysms ◽  
Cfd Models ◽  
Increased Risk ◽  
Risk Of Rupture ◽  
Bleb Formation

Abstract BACKGROUND: The management of unruptured aneurysms is controversial, with the decision to treat influenced by aneurysm characteristics including size and morphology. Aneurysmal bleb formation is thought to be associated with an increased risk of rupture. OBJECTIVE: To correlate computational fluid dynamic (CFD) indices with bleb formation. METHODS: Anatomic models were constructed from 3-dimensional rotational angiography data in 27 patients with cerebral aneurysms harboring a single bleb. Additional models representing the aneurysm before bleb formation were constructed by digitally removing the bleb. We characterized hemodynamic features of models both with and without the blebs using CFDs. Flow structure, wall shear stress (WSS), pressure, and oscillatory shear index (OSI) were analyzed. RESULTS: There was a statistically significant association between bleb location at or adjacent to the point of maximal WSS (74%, P = .019), irrespective of rupture status. Aneurysmal blebs were related to the inflow or outflow jet in 89% of cases (P &lt; .001), whereas 11% were unrelated. Maximal wall pressure and OSI were not significantly related to bleb location. The bleb region attained a lower WSS after its formation in 96% of cases (P &lt; .001) and was also lower than the average aneurysm WSS in 86% of cases (P &lt; .001). CONCLUSION: Cerebral aneurysm blebs generally form at or adjacent to the point of maximal WSS and are aligned with major flow structures. Wall pressure and OSI do not contribute to determining bleb location. The measurement of WSS using CFD models may potentially predict bleb formation and thus improve the assessment of rupture risk in unruptured aneurysms.

scholarly journals Summary on the Results of Two Computational Fluid Dynamic Benchmarks of Tube and Different Channel Geometries

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Attila Kiss ◽  
Andrey Churkin ◽  
Darwan S. Pilkhwal ◽  
Abhijeet M. Vaidya ◽  
Walter Ambrosini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Computational Fluid Dynamic ◽  
Prediction Accuracy ◽  
Fluid Dynamic ◽  
Annular Channel ◽  
Initial Boundary ◽  
Sensitivity Analyses ◽  
Cfd Models

Two computational fluid dynamic (CFD) benchmarks have been performed to assess the prediction accuracy and sensitivity of CFD codes for heat transfer in different geometries. The first benchmark focused on heat transfer to water in a tube (first benchmark), while the second benchmark covered heat transfer to water in two different channel geometries (second benchmark) at supercritical pressures. In the first round with the experimental data unknown to the participants (i.e., blind calculations), CFD calculations were conducted with initial boundary conditions and simpler CFD models. After assessment against measurements, the calculations were repeated with the refined boundary conditions and material properties in the follow-up calculation phase. Overall, the CFD codes seem to be able to capture the general trend of heat transfer in the tube and the annular channel but further improvements are required in order to enhance the prediction accuracy. Finally, sensitivity analyses on the numerical mesh and the boundary conditions were performed. It was found that the prediction accuracy has not been improved with the introduction of finer meshes and the effect of mass flux on the result is the strongest among various investigated boundary conditions.

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