UFR 2-11 Test Case

High Reynolds Number Flow around Airfoil in Deep Stall

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Test Case Study

Brief Description of the Test Case

The following presents a precise description of the primary test case, the NACA0021 airfoil at 60° angle of attack.

A visual impression of the geometry and flow has been shown in Figure 1. The experiments were carried out in the wind tunnel of Monash University (see Figure 2). The width of the experimental section is 7.2 airfoil chord lengths, c, and its height is 16c.

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Figure 2: NACA0021 airfoil in wind tunnel (left) and a plan view of wind tunnel (right) [ ]

The airfoil geometry normalized with the chord length, c, is defined by:

${y=\pm {\frac {0.21}{0.2}}\left(0.2969\ {\sqrt {x}}-0.126\ x-0.3516\ x^{2}+0.2846\ x^{3}-0.1015\ x^{4}\right)}$

Experimental flow parameters, needed to set up appropriate numerical simulations, are presented in Table 2.

Table 2: Flow parameters

Parameter	Notation	Value
Reynolds number	${Re=U_{\infty }c/\nu }$	2.7×105
Chord length	$\left.c\right.$	0.125 m
Angle of attack	$\left.\alpha \right.$	60°
Free stream Mach number	$\left.M\right.$	0.1
Free stream streamwise turbulence intensity	$\left.l_{u}\right.$	0.6%

The flow parameters measured in the experiments are as follows:

• Time-averaged pressure coefficient distribution over the airfoil surface, ${C_{p}(x)={\frac {p-p_{\infty }}{{\frac {1}{2}}\rho U_{\infty }^{2}c}}}$, where $\left.p_{\infty }\right.$ is the reference pressure from the undisturbed far-field flow and $\left.\rho \right.$ is the fluid density.

• Time-averaged sectional drag and lift coefficients, $\left.C_{d},\ C_{l}\right.$ integrated from pressure at individual spanwise locations near the spanwise mid-point: ${C_{d}={\frac {d}{{\frac {1}{2}}\rho U_{\infty }^{2}c}},\ C_{l}={\frac {l}{{\frac {1}{2}}\rho U_{\infty }^{2}c}}}$, where $\left.d\right.$ and $\left.l\right.$ are the sectional pressure drag and lift forces, respectively.

• Time histories of the sectional lift and drag coefficients (32,000 points total over the time interval T≈9000 (c/U₀)).

CFD Methods

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Contributed by: Charles Mockett; Misha Strelets — CFD Software GmbH and Technische Universitaet Berlin; New Technologies and Services LLC (NTS) and Saint-Petersburg State University

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