Helicopter Blade NACA 8H12 Performance Prediction with Laminar-Turbulent Transition Effects: Integral Boundary-Layer and CFD Results compared with Experimental Data

2015 ◽  
Author(s):  
Guilherme A. Silva ◽  
Donizeti de Andrade ◽  
Caio F. Rafael ◽  
Diogo M. Pio
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Performance Prediction ◽  
Integral Boundary ◽  
Helicopter Blade ◽  
Turbulent Transition ◽  
Transition Effects ◽  
Laminar Turbulent Transition

One-Dimensional Performance Prediction of Subsonic Vaned Diffusers

1999 ◽  
Author(s):  
Beat Ribi ◽  
Peter Dalbert
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Performance Prediction ◽  
Performance Characteristic ◽  
Continuity Equation ◽  
Pressure Rise ◽  
Prediction Method ◽  
Momentum Thickness ◽  
Integral Boundary ◽  
One Dimensional

A simple 1-d-theory to predict the performance of a diffuser using as few empirical factors as possible is presented. The prediction method uses two empirical functions to assess both the pressure recovery and the losses. The functions have been calibrated from experimental data from the company’s standard diffusers. The method is, however, adaptable for any type of subsonic vaned diffusers provided that the empirical functions can be calibrated from measurements. The pressure rise in the diffuser is calculated from the continuity equation taking into account the blockage, while the losses are determined by means of displacement and momentum thickness. These values are calculated at design point from an integral boundary layer calculation. To take into account the influence of flow separation at off-design the calculated displacement and momentum thickness are increased according to empirical functions. When designing a new impeller the method provides a simple way to evaluate the diffuser resulting in the best combination in terms of efficiency and range. It further provides a simple means of estimating the change to be expected in a known stage performance characteristic due to a modification of the diffuser geometry.

scholarly journals Simulation of a laminar-turbulent flow in three-dimensional aerodynamic configurations

2021 ◽  
Vol 2057 (1) ◽  
pp. 012080
Author(s):  
T V Poplavskaya ◽  
A V Boiko ◽  
K V Demyanko ◽  
S V Kirilovskiy ◽  
Y M Nechepurenko
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Prolate Spheroid ◽  
Turbulent Transition ◽  
Good Agreement ◽  
Laminar Turbulent Transition

Abstract The goal of the paper is to determine the position of the laminar-turbulent transition in the boundary layer of a prolate spheroid using the eN-method with the calibration of threshold N-factors. It is demonstrated that the predicted and experimental data on the laminarturbulent transition are in good agreement.

One-Dimensional Performance Prediction of Subsonic Vaned Diffusers

1999 ◽  
Vol 122 (3) ◽  
pp. 494-504 ◽  
Author(s):  
Beat Ribi ◽  
Peter Dalbert
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Performance Prediction ◽  
Continuity Equation ◽  
Pressure Rise ◽  
Prediction Method ◽  
Momentum Thickness ◽  
Dimensional Theory ◽  
Integral Boundary ◽  
One Dimensional

A simple one-dimensional theory to predict the performance of a diffuser using as few empirical factors as possible is presented. The prediction method uses two empirical functions to assess both the pressure recovery and the losses. The functions have been calibrated from experimental data from the company’s standard diffusers. The method is, however, adaptable for any type of subsonic vaned diffusers, provided that the empirical functions can be calibrated from measurements. The pressure rise in the diffuser is calculated from the continuity equation, taking into account the blockage, while the losses are determined by means of displacement and momentum thickness. These values are calculated at design point from an integral boundary layer calculation. To take into account the influence of flow separation at off-design, the calculated displacement and momentum thickness are increased according to empirical functions. When designing a new impeller, the method provides a simple way to evaluate the diffuser, resulting in the best combination in terms of efficiency and range. It further provides a simple means of estimating the change to be expected in a known stage performance characteristic due to a modification of the diffuser geometry.[S0889-504X(00)01703-7]

INFLUENCE OF THE PLATE LEADING-EDGE SHAPE AND THICKNESS ON THE BOUNDARY LAYER LAMINAR-TURBULENT TRANSITION IN HYPERSONIC FLOW

2019 ◽  
Vol 50 (5) ◽  
pp. 461-481
Author(s):  
Sergei Vasilyevich Aleksandrov ◽  
Evgeniya Andreevna Aleksandrova ◽  
Volf Ya. Borovoy ◽  
Andrey Vyacheslavovich Gubernatenko ◽  
Vladimir Evguenyevich Mosharov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Hypersonic Flow ◽  
Leading Edge ◽  
Turbulent Transition ◽  
Laminar Turbulent Transition

scholarly journals Investigation of Laminar–Turbulent Transition on a Rotating Wind-Turbine Blade of Multimegawatt Class with Thermography and Microphone Array

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2102 ◽  
Author(s):  
Torben Reichstein ◽  
Alois Peter Schaffarczyk ◽  
Christoph Dollinger ◽  
Nicolas Balaresque ◽  
Erich Schülein ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Turbine ◽  
Microphone Array ◽  
Suction Side ◽  
Flow Transition ◽  
Turbulent Transition ◽  
Start Up ◽  
Open Question ◽  
Laminar Turbulent Transition

Knowledge about laminar–turbulent transition on operating multi megawatt wind turbine (WT) blades needs sophisticated equipment like hot films or microphone arrays. Contrarily, thermographic pictures can easily be taken from the ground, and temperature differences indicate different states of the boundary layer. Accuracy, however, is still an open question, so that an aerodynamic glove, known from experimental research on airplanes, was used to classify the boundary-layer state of a 2 megawatt WT blade operating in the northern part of Schleswig-Holstein, Germany. State-of-the-art equipment for measuring static surface pressure was used for monitoring lift distribution. To distinguish the laminar and turbulent parts of the boundary layer (suction side only), 48 microphones were applied together with ground-based thermographic cameras from two teams. Additionally, an optical camera mounted on the hub was used to survey vibrations. During start-up (SU) (from 0 to 9 rpm), extended but irregularly shaped regions of a laminar-boundary layer were observed that had the same extension measured both with microphones and thermography. When an approximately constant rotor rotation (9 rpm corresponding to approximately 6 m/s wind speed) was achieved, flow transition was visible at the expected position of 40% chord length on the rotor blade, which was fouled with dense turbulent wedges, and an almost complete turbulent state on the glove was detected. In all observations, quantitative determination of flow-transition positions from thermography and microphones agreed well within their accuracy of less than 1%.

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