Abstract
A technique is described and the results of an experimental study of the aerodynamic structure of turbulent streamlining, velocity fluctuations, and pressure fields on the surface of a single trench dimple located on the wall of a flat rectangular channel are presented. The trench dimple cross section is a cylindrical segment with hemispheres at its edges. The measurements were carried out with a two-component laser-Doppler anemometer at two angles of the dimple inclination relative to the flow direction φ = 0 and 45°. The development of the flow in the direction transverse to the trench, as well as along it, was studied. The fundamental difference between the velocity fields and their fluctuations in a trench located normally and at an angle to the flow is shown.
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Abbreviations
- a :
-
channel width, m
- C f/2:
-
channel friction coefficient
- C p = 2∧p/(ρU m 2):
-
pressure coefficient
- D :
-
dimple width, m (determined in Fig. 1)
- D ch :
-
channel hydraulic diameter, m
- H :
-
channel height, m
- L :
-
dimple length, m
- n :
-
exponent of power dependence of velocity on height in the channel
- p :
-
static pressure, Pa
- U m :
-
mass average velocity in the channel, m/s
- U* = U 0(C f/2)1/2 :
-
friction velocity (dynamic velocity), m/s
- U 0 :
-
maximum velocity in the channel, m/s
- U z, V x :
-
velocity components along z and x axes, m/s
- U t, V s :
-
velocity components along t and s axes, m/s
- x, y, z :
-
Cartesian coordinate system
- y′ :
-
axis connected to the trench bottom (determined in Fig. 1)
- δ* :
-
displacement thickness of a boundary layer, m
- R :
-
dimple radius, m
- ReD :
-
Reynolds number, determined from dimple width D
- Rech :
-
Reynolds number, determined from channel hydraulic diameter Dch
- t, s :
-
dimple coordinate system (determined in Fig. 1)
- T :
-
air temperature, °C
- Δ:
-
dimple depth (determined in Fig. 1)
- η = y′U*/ν :
-
universal dimensionless coordinate
- ν :
-
kinematic viscosity, m2/s
- ρ :
-
air density, kg/m3
- φ :
-
dimple inclination angle, deg (determined in Fig. 1).
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The work was financially supported by the Russian Science Foundation (Grant No. 21-19-00162).
The authors are grateful to S.A. Isaev for useful discussions of research.
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Terekhov, V.I., Terekhov, V.V., Chokhar, I.A. et al. Experimental investigation of the flow structure in a single trench dimple. Thermophys. Aeromech. 29, 887–898 (2022). https://doi.org/10.1134/S0869864322060087
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DOI: https://doi.org/10.1134/S0869864322060087