For laminar boundary layers it is reasonable to expect that δ /δt ≈ prn, where n is a positive exponent. consider laminar boundary layer flow over a flat plate with air at 100ºc and 1 atm, the thermal boundary layer thickness is approximately 15% larger than the velocity boundary layer thickness. determine the ratio of δ/δt if the fluid is engine oil (unused) under the same flow conditions. (round the final answer to two decimal place.) given: for air at 100ºc and 1 atm, pr = 0.7111. for engine oil (unused) at 100ºc, pr = 279.1