18) EXAMPLE PROBLEM GIVEN: Numerical solution for laminar flat-plate boundary layer, Table 9.1. Blasius Solution
FIND: bw/U at boundary-layer edge. (c) Ratio of the slope of a streamline at the boundary-layer edge to the slope of θ versus x.
19) Part A. Choose the right answer (ONLY ONE):
1. The boundary layer thickness δ can be approximately scaled as: [a] νL/U [b] L/ReL [c] Vvt [d] All of them
2. The Prandtl boundary layer differential equations are classified as: [a] Elliptic [b] Parabolic [c] Hyperbolic [d] None of them
3. What kind of approach would be sufficient to solve for the lift coefficient over an airfoil: [a] Potential flow [b] Parallel flow [c] Low-Reynolds Number flow [d] All of them
Part B. Air at 20°C at 1 atm (Ï = 1.2 kg/m³, μ = 1.8E-5 kg/m.s) flows at 20 m/s past the flat plate, as shown in the figure. A pitot stagnation tube, placed 2 mm from the wall, develops a manometer head h = 16 mm of Meriam oil, SG = 0.827. Estimate the position of the pitot tube, assuming laminar incompressible flow, then solve for the exact boundary layer thickness δE at this position.
n = yU/vx^(1/2) 0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0
f(n) = 0 0.02656 0.10611 0.23795 0.42032 0.65003 0.92230 1.23099 1.56911 1.92954 2.30576
f(n) = u/U 0 0.13277 0.26471 0.39378 0.51676 0.62977 0.72899 0.81152 0.87609 0.92333 0.95552
(W.J) = 0.33206 0.33147 0.32739 0.31659 0.29667 0.26675 0.22809 0.18401 0.13913 0.09809 0.06424
Boundary layer
20 m/s
4
2 mm
h