Experimental investigation of viscous drag reduction of superhydrophobic nano-coating in laminar and turbulent flows

2013 ◽  
Vol 51 ◽  
pp. 239-243 ◽  
Author(s):  
Kh. Moaven ◽  
M. Rad ◽  
M. Taeibi-Rahni
Keyword(s):  
Experimental Investigation ◽  
Drag Reduction ◽  
Turbulent Flows ◽  
Viscous Drag ◽  
Nano Coating ◽  
Laminar And Turbulent Flows

Heat Transfer and Drag Reduction in Flows Over Riblet Mounted Surfaces

2003 ◽  
Author(s):  
Stefan aus der Wiesche
Keyword(s):  
Heat Transfer ◽  
Drag Reduction ◽  
Turbulent Flows ◽  
Numerical Data ◽  
Smooth Wall ◽  
Reynolds Analogy ◽  
Turbulent Drag ◽  
Prandtl Numbers ◽  
Laminar And Turbulent Flows ◽  
Good Agreement

The heat transfer in a channel with its lower wall mounted with streamwise V-shaped riblets is investigated numerically using a LES approach. Both laminar and turbulent flows are considered. At the riblet wall the turbulent drag is reduced by 6% in comparison to the smooth wall, whereas for laminar flow the riblets lead to a significant drag increase. The effect of riblets on heat transfer is investigated explicitly for small Prandtl numbers Pr and an appropriate correlation is derived. This correlation indicates that the Reynolds analogy is not violated in case of Pr = 1 despite the extraordinary turbulent drag reducing mechanism. The numerical results for drag reduction are in good agreement with available experimental and numerical data, and the results are faced with corresponding heat transfer results found in the literature.

Drag reduction by spanwise wall oscillation in wall-bounded turbulent flows

AIAA Journal ◽  
2002 ◽  
Vol 40 ◽  
pp. 842-850 ◽  
Author(s):  
J.-I. Choi ◽  
C.-X. Xu ◽  
H. J. Sung
Keyword(s):  
Drag Reduction ◽  
Turbulent Flows ◽  
Wall Oscillation

Drag reduction capability of uniform blowing in supersonic wall-bounded turbulent flows

2017 ◽  
Vol 2 (12) ◽  
Author(s):  
Yukinori Kametani ◽  
Ayane Kotake ◽  
Koji Fukagata ◽  
Naoko Tokugawa
Keyword(s):  
Drag Reduction ◽  
Turbulent Flows

A numerical study on combined baffles quick-separation device

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ehsan Dehdarinejad ◽  
Morteza Bayareh ◽  
Mahmud Ashrafizaadeh
Keyword(s):  
Turbulent Flows ◽  
Separation Efficiency ◽  
Numerical Study ◽  
Turbulence Models ◽  
Complete Separation ◽  
Solid Particles ◽  
Flow Rates ◽  
Separation Device ◽  
Coupling Technique ◽  
Laminar And Turbulent Flows

Abstract The transfer of particles in laminar and turbulent flows has many applications in combustion systems, biological, environmental, nanotechnology. In the present study, a Combined Baffles Quick-Separation Device (CBQSD) is simulated numerically using the Eulerian-Lagrangian method and different turbulence models of RNG k-ε, k-ω, and RSM for 1–140 μm particles. A two-way coupling technique is employed to solve the particles’ flow. The effect of inlet flow velocity, the diameter of the splitter plane, and solid particles’ flow rate on the separation efficiency of the device is examined. The results demonstrate that the RSM turbulence model provides more appropriate results compared to RNG k-ε and k-ω models. Four thousand two hundred particles with the size distribution of 1–140 µm enter the device and 3820 particles are trapped and 380 particles leave the device. The efficiency for particles with a diameter greater than 28 µm is 100%. The complete separation of 22–28 μm particles occurs for flow rates of 10–23.5 g/s, respectively. The results reveal that the separation efficiency increases by increasing the inlet velocity, the device diameter, and the diameter of the particles.

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