Measurement of the Wall Shear Stress With Sublayer Thin Plate of Thermochromic Liquid Crystal

2015 ◽  
Author(s):  
Takashi Kodama ◽  
Shinsuke Mochizuki
Keyword(s):  
Shear Stress ◽  
Liquid Crystal ◽  
Friction Coefficient ◽  
Wall Shear Stress ◽  
Skin Friction ◽  
Channel Flow ◽  
Skin Friction Coefficient ◽  
Local Skin ◽  
Local Skin Friction ◽  
Wall Shear

New optical method for measurement of the local wall shear stress has been developed by using thermo-chromic liquid crystal temperature measurement based on hue [1], [2] of the camera view. The flow field is the fully developed turbulent channel flow. Thin film made of thermo-chromic liquid crystal is placed on the wall. A rectangular shaped obstacle is glued on the film. The obstacle is within a region of buffer layer with height from the wall. Temperature of the film and the obstacle are slightly raised by a heater below the wall. The air flow makes non-uniform temperature distribution and non-uniform color distribution appears on the surface of the film. Relations between hue and local skin friction coefficient were examined in a turbulent air channel flow. It is indicated that a certain hue of a point is varying linearly against the corresponding local skin friction coefficient.

scholarly journals Effects of Slip and Heat Generation/Absorption on MHD Mixed Convection Flow of a Micropolar Fluid over a Heated Stretching Surface

2010 ◽  
Vol 2010 ◽  
pp. 1-20 ◽  
Author(s):  
Mostafa Mahmoud ◽  
Shimaa Waheed
Keyword(s):  
Nusselt Number ◽  
Friction Coefficient ◽  
Mixed Convection ◽  
Skin Friction ◽  
Heat Generation ◽  
Local Nusselt Number ◽  
Skin Friction Coefficient ◽  
Convection Flow ◽  
Local Skin ◽  
Local Skin Friction

A theoretical analysis is performed to study the flow and heat transfer characteristics of magnetohydrodynamic mixed convection flow of a micropolar fluid past a stretching surface with slip velocity at the surface and heat generation (absorption). The transformed equations solved numerically using the Chebyshev spectral method. Numerical results for the velocity, the angular velocity, and the temperature for various values of different parameters are illustrated graphically. Also, the effects of various parameters on the local skin-friction coefficient and the local Nusselt number are given in tabular form and discussed. The results show that the mixed convection parameter has the effect of enhancing both the velocity and the local Nusselt number and suppressing both the local skin-friction coefficient and the temperature. It is found that local skin-friction coefficient increases while the local Nusselt number decreases as the magnetic parameter increases. The results show also that increasing the heat generation parameter leads to a rise in both the velocity and the temperature and a fall in the local skin-friction coefficient and the local Nusselt number. Furthermore, it is shown that the local skin-friction coefficient and the local Nusselt number decrease when the slip parameter increases.

Non-similar characteristics of mixed convective slip flow over a wedge with temperature-dependent thermo-physical properties

2019 ◽  
Vol 33 (36) ◽  
pp. 1950455
Author(s):  
Nepal Chandra Roy ◽  
Sudharonjon Roy ◽  
Naved Azum ◽  
Anish Khan ◽  
Abdullah M. Asiri ◽  
...  
Keyword(s):  
Nusselt Number ◽  
Friction Coefficient ◽  
Skin Friction ◽  
Sherwood Number ◽  
Local Nusselt Number ◽  
Slip Flow ◽  
Skin Friction Coefficient ◽  
Local Skin ◽  
Local Skin Friction ◽  
Local Sherwood Number

We examined heat and mass transfer characteristics of mixed convective slip flow over a wedge taking into account the effect of variable transport properties. Unlike other studies, we have utilized non-similar transformation to get the non-similar features of the mixed convective slip flow. For comparison, stream function formulation is used to reduce the governing equation into a convenient form for short- and long-time regimes. We have determined the series solutions by adopting the perturbation techniques. The agreement between the numerical and series solutions is found to be excellent. Numerical solutions reveal that the slip parameters augment the momentum, thermal and concentration boundary layers. The local skin friction coefficient, the local Nusselt number and the local Sherwood number are found to decrease for higher value of slip parameters. For the increasing value of the variable viscosity parameter, the velocity is stronger, but the temperature and concentration lessen. Contrary to this, this parameter diminishes the local skin friction coefficient, local Nusselt number and local Sherwood number. Due to the increase of mass diffusivity parameter, the velocity and concentration significantly increase whereas the temperature remains almost unaffected. Moreover, the mass diffusivity variation parameter leads to an increase in the local skin friction coefficient and local Nusselt number, but it reduces the local Sherwood number.

Skin Friction Coefficient and Boundary Layer Trend on UKM Aster i-Bond

2014 ◽  
Vol 629 ◽  
pp. 450-455
Author(s):  
Zambri Harun ◽  
Muhammad Syafiq ◽  
Mohd Rasidi Rasani ◽  
Shahrum Abdullah ◽  
Rozli Zulkifli ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Skin Friction ◽  
Aerodynamic Drag ◽  
Skin Friction Coefficient ◽  
Front Part ◽  
Rear Part ◽  
Wall Shear ◽  
Cfd Method

This study concerns with aerodynamic drag on a passenger car. By using computational fluid dynamics (CFD) method, we found that values of skin friction coefficients for three different parts of the car: front, top and rear parts, are different. This study addresses three different basic possible flows around a car: favourable, zero and adverse pressure gradients. Generally, cars use approximately 20% of their engine power to overcome aerodynamic drag, which is generally proportional to the frontal area. The boundary layer at each position has been analyzed to ascertain the effect of wall shear stress on the car surface. It is found that the value of wall shear stress velocity is highest at the rear part, followed by front and top parts. Subsequently, it is shown that the front part has the thinnest viscous region despite not being the part with the highest local ambient velocity compared with the top and rear parts. Despite its supposed aerodynamic shape, the rear part of the car sees separation of flow and the total drag per unit area here is the largest, twice as large as front part and more than seven times larger than the top part.

Natural Convective Boundary Layer Flow of Nanofluids Above an Isothermal Horizontal Plate

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Kaustav Pradhan ◽  
Subho Samanta ◽  
Abhijit Guha
Keyword(s):  
Nusselt Number ◽  
Friction Coefficient ◽  
Skin Friction ◽  
Volume Fraction ◽  
Skin Friction Coefficient ◽  
Nanoparticle Volume Fraction ◽  
Convective Boundary ◽  
Local Skin ◽  
Local Skin Friction ◽  
Layer Flow

The natural convective boundary layer flow of a nanofluid over an isothermal horizontal plate is studied analytically. The model used for the nanofluid accounts for the effects of Brownian motion and thermophoresis. The analysis shows that the velocity, temperature, and nanoparticle volume fraction profiles in the respective boundary layers depend not only on the Prandtl number (Pr) and Lewis number (Le) but also on three additional dimensionless parameters: the Brownian motion parameter Nb, the buoyancy ratio parameter Nr and the thermophoresis parameter Nt. The velocity, temperature, and nanoparticle volume fraction profiles for the nanofluid are found to have a weak dependence on the values of Nb, Nr, and Nt. The effect of the above-mentioned parameters on the local skin-friction coefficient and Nusselt number has been studied extensively. It has been observed that as Nr increases, the local skin-friction coefficient decreases whereas local Nusselt number remains almost constant. As Nb or Nt increases, the local skin-friction coefficient increases whereas the local Nusselt number decreases.

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