scholarly journals Estimation of three-dimensional aerodynamic damping using CFD

2019 ◽  
Vol 124 (1271) ◽  
pp. 24-43 ◽  
Author(s):  
R.J. Higgins ◽  
G.N. Barakos ◽  
E. Jinks
Keyword(s):  
Three Dimensional ◽  
Separated Flow ◽  
Turbulence Closure ◽  
Flow Structures ◽  
Test Cases ◽  
Aerodynamic Damping ◽  
Initial Investigation ◽  
Time Marching ◽  
Negative Damping ◽  
Naca 0012

AbstractAeroelastic phenomena of stall flutter are the result of the negative aerodynamic damping associated with separated flow. From this basis, an investigation has been conducted to estimate the aerodynamic damping from a time-marching aeroelastic computation. An initial investigation is conducted on the NACA 0012 aerofoil section, before transition to 3D propellers and full aeroelastic calculations. Estimates of aerodynamic damping are presented, with a comparison made between URANS and SAS. Use of a suitable turbulence closure to allow for shedding of flow structures during stall is seen as critical in predicting negative damping estimations. From this investigation, it has been found that the SAS method is able to capture this for both the aerofoil and 3D test cases.

Three-dimensional Separated Flow Structures

1987 ◽  
pp. 387-389
Author(s):  
U. Dallmann ◽  
W. Kordulla ◽  
H. Vollmers
Keyword(s):  
Three Dimensional ◽  
Separated Flow ◽  
Flow Structures

Application of a Viscous Through-Flow Model to a Modern Axial Low-Pressure Compressor

2021 ◽  
Author(s):  
Arnaud Budo ◽  
Vincent E. Terrapon ◽  
Maarten Arnst ◽  
Koen Hillewaert ◽  
Sophie Mouriaux ◽  
...  
Keyword(s):  
Flow Model ◽  
Three Dimensional ◽  
Test Case ◽  
Test Cases ◽  
Compressor Stage ◽  
Flow Solver ◽  
Closure Models ◽  
Through Flow ◽  
Time Marching ◽  
Pressure Compressor

Abstract This paper describes the evaluation of a newly developed viscous time-marching through-flow solver to two test cases to assess the applicability of the method using correlations from the literature to modern blade designs. The test cases are the classic axial compressor stage CME2 and a modern highly loaded multi-stage axial low-pressure compressor developed by Safran Aero Boosters. The through-flow solver is based on the Navier-Stokes equations and uses a pseudo-time marching method. The closure models currently include terms of major importance: the blade forces and the Reynolds stress. The results are compared to higher-fidelity results including three-dimensional RANS simulations to assess their reliability for design and off-design conditions. The main originality of this work is the evaluation of the CFD-based method in the context of a compressor with highly three-dimensional blades, as such an analysis is not commonly found in the literature. The solver gives realistic predictions of loss and deviation for the compressor stage CME2 at both design and off-design operating conditions. Regarding the second test case, the through-flow simulations based on theoretically non-adapted correlations for such a compressor are still in good agreement with RANS simulations, although the results for the 2nd test case are probably not as good as for the first. These results are a promising first step towards the use of this through-flow model for industrial design. Regarding the ongoing closure models development, suggestions to extend the loss models to a larger range of designs are discussed.

scholarly journals Unsteady RANS Simulations of Strong and Weak 3D Stall Cells on a 2D Pitching Aerofoil

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 40 ◽  
Author(s):  
Dajun Liu ◽  
Takafumi Nishino
Keyword(s):  
Lift Coefficient ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Navier Stokes ◽  
Flow Structures ◽  
Computational Domain ◽  
Rans Simulations ◽  
Stall Cells ◽  
Naca 0012

A series of three-dimensional unsteady Reynolds-averaged Navier–Stokes (RANS) simulations are conducted to investigate the formation of stall cells over a pitching NACA 0012 aerofoil. Periodic boundary conditions are applied to the spanwise ends of the computational domain. Several different pitching ranges and frequencies are adopted. The influence of the pitching range and frequency on the lift coefficient (CL) hysteresis loop and the development of leading-edge vortex (LEV) agrees with earlier studies in the literature. Depending on pitching range and frequency, the flow structures on the suction side of the aerofoil can be categorized into three types: (i) strong oscillatory stall cells resembling what are often observed on a static aerofoil; (ii) weak stall cells which are smaller in size and less oscillatory; and (iii) no stall cells at all (i.e., flow remains two-dimensional) or only very weak oval-shaped structures that have little impact on CL. A clear difference in CL during the flow reattachment stage is observed between the cases with strong stall cells and with weak stall cells. For the cases with strong stall cells, arch-shaped flow structures are observed above the aerofoil. They resemble the Π-shaped vortices often observed over a pitching finite aspect ratio wing.

scholarly journals Automatized Evaluation of Students’ CAD Models

2021 ◽  
Vol 11 (4) ◽  
pp. 145
Author(s):  
Nenad Bojcetic ◽  
Filip Valjak ◽  
Dragan Zezelj ◽  
Tomislav Martinec
Keyword(s):  
Computer Aided Design ◽  
Three Dimensional ◽  
Computer Application ◽  
Test Cases ◽  
Cad Model ◽  
Computer Solution ◽  
3D Cad ◽  
Computer Aided ◽  
Cad Models ◽  
Aided Design

The article describes an attempt to address the automatized evaluation of student three-dimensional (3D) computer-aided design (CAD) models. The driving idea was conceptualized under the restraints of the COVID pandemic, driven by the problem of evaluating a large number of student 3D CAD models. The described computer solution can be implemented using any CAD computer application that supports customization. Test cases showed that the proposed solution was valid and could be used to evaluate many students’ 3D CAD models. The computer solution can also be used to help students to better understand how to create a 3D CAD model, thereby complying with the requirements of particular teachers.

scholarly journals Experimental Study on Coherent Structures by Particles Suspended in Half-Zone Thermocapillary Liquid Bridges: Review

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 105
Author(s):  
Ichiro Ueno
Keyword(s):  
Coherent Structures ◽  
Three Dimensional ◽  
Wave Number ◽  
Flow Structures ◽  
Liquid Bridges ◽  
Thermocapillary Effect ◽  
Particle Accumulation ◽  
Azimuthal Wave Number ◽  
Experimental Approaches ◽  
Particle Behaviour

Coherent structures by the particles suspended in the half-zone thermocapillary liquid bridges via experimental approaches are introduced. General knowledge on the particle accumulation structures (PAS) is described, and then the spatial–temporal behaviours of the particles forming the PAS are illustrated with the results of the two- and three-dimensional particle tracking. Variations of the coherent structures as functions of the intensity of the thermocapillary effect and the particle size are introduced by focusing on the PAS of the azimuthal wave number m=3. Correlation between the particle behaviour and the ordered flow structures known as the Kolmogorov–Arnold—Moser tori is discussed. Recent works on the PAS of m=1 are briefly introduced.

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