Plate friction coefficient

Momentum boundary layer calculations are useful to estimate the skin friction on a number of objects, such as on a ship hull, airplane fuselage and wings, a water surface, and a terrestrial surface. Once we know the boundary layer thickness, occurring where the velocity is 99% of the free-stream velocity, skin friction coefficient and the skin friction drag on the solid surface can be calculated. Estimate the laminar boundary layer thickness of a 1-m-long, thin flat plate moving through a calm atmosphere at 20 m/s. 

Table E4.4.1 Boundary layer thickness and skin friction coefficient for aflat plate moving at 20 m/s in the atmosphere...

When the inlet length is expressed in terms of number of gap widths , the difference between the flow in a tube and the flow in an annulus of narrow gap differs only by 25% [(0.05 - 0.04)/0.05]. This situation is an indication that the growth of the laminar boundary layers from the wall to the center of the channel is similar in both cases. Because duct friction coefficients, a measure of momentum transfer, do not vary by more than a factor of 2 for ducts of regular cross sections when expressed in terms of hydraulic diameters, the use of the inlet length for tubes or parallel plates can be expected to be a reasonable approximation for the inlet lengths of other cross sections under laminar flow conditions. In the annular denuder, the dimensionless inlet length for laminar flow development, L, can be expressed as... 

A block of metal with a mass of 5 kg is put on an plate of the same metal 1 meter from the left end of the plate. The coefficient of static friction of the material is 0.5,the coefficient of kinetic friction is 0.4. The right end of the plate is slowly being lifted to incline the plate until the block begins to slide. At which inclination angle does the block begin to slide If the plate is kept at this angle, what speed will the block have when it reaches the left end of the plate ... 

Two ions each with z = 2 but with slightly different friction coefficients (averaging 5 x 1015 g/s) require 25,000 plates for separation. What voltage drop is needed How long does the separation take when executed over a 10.0 cm path length 50.0 cm Assume 0 = 1 and T = 290 K. (Watch your units )... 

Schlichting [1] has surveyed experimental measurements of friction coefficients for turbulent flow on flat plates. We present the results of that survey so that they may be employed in the calculation of turbulent heat transfer with the fluid-friction-heat-transfer analogy. The local skin-friction coefficient is given by... 

The average-friction coefficient for a flat plate with a laminar boundary layer up to Recrii and turbulent thereafter can be calculated from... 

Nitrogen at 1 atm and 20°C is blown across a 130-cm-square flat plate at a velocity of 3.0 m/s. The plate is maintained at a constant temperature of lOO C. Calculate the average-friction coefficient and the heat transfer from the plate. 

The effects of the composite parameter WjFM on the friction coefficient of the contact lens coated by methane plasma polymer at a fixed coating thickness 31.2nm are shown in Figure 35.3. The friction coefficient, which is the tangential force divided by the normal force, was calculated from the sliding angle of a contact lens placed on a glass plate that was coated with plasma polymer of tetrafluoroethylene (TFE). The friction coefficient of the methane plasma polymerized contact lens is independent of WjFM in the range 2.6-29.1 GJ/kg. 

Friction Coefficient 400 Heat Transfer Coefficient 401 Flat Plate with Unhealed Starting I engih 403 Uniform Heat Flux 403... 

The friction coefficient and Nusselt number for a flat plate were determined in Section 6-8 to be... 

For flat plates, the drag force is equivalent to friction force. The average friction coefficient Qcan be determined from Eq. 6-11,... 

C What does the friction coefficient represent in flow over a flat plate How is it related to the drag force acting on the plate ... 

Once the average friction coefficient C is available, the drag (or friction) force over the surface can be determined from Rq. 7-1. In this case/1 is the surface area of the plate exposed to fluid flow. When both side.s of a thin plate are subjected to flow, A becomes the total area of the top and bottom surfaces. Note that the friction coefficient, in general, varies with location along the surface. 

For parallel flow over a flat plate, the pressure drag is zero, and thus the drag coefficient is equal to the friction coefficient and the drag force is equal to the friction force. 

The average friction coefficient over the entire plate is determined by substituting the relations above into Eq. 7-7 and performing the integrations (Fig. 7-7). We get... 

The first relation gives the average friction coefficient for the entire plate when the flow is laminar over the entire plate. The second relation gives the average friction coefficient for the entire plate only when Ihe flow is turbulent over the entire plate, or when the laminar flow region of the plate is too small relative to the tuibulent flow region (that is,. t < L). 

The average friction coefficient relations for flow over a flat plate are ... 

C Consider InniiniU flow over a flat plate. Will the friction coefficient change with distance from the leading edge How about the heat Iransfer coefficient ... 

Figure 24a, b show the frictional forces (F) and frictional coefficient (jU ) of the three kinds of gels as a function of normal pressure (P) [61], The gels were slid on the glass plate in water. The results clearly shows that the frictional coefficient decreases in the order DN > TN > DN-L, indicating that introduction of PAMPS, especial linear PAMPS, as the third network component obviously reduces the frictional coefficient of the gels. 

The total friction coefficient for a plate of length L is given by the formula 1 1 798... 

Consider a flat plate steadily oscillating with velocity V0 sin cat on top of another flat plate (Fig. 3P-4). The pressure and dry friction coefficient between the plate are p and pc, respectively. Find the steady periodic temperature fluctuations in the system. 

---