Accession Number : ADA540295


Title :   A Realistic Theoretical Model for Laminar Flow over a Flat Plate


Descriptive Note : Technical rept. 1 Jan-1 Sep 2010


Corporate Author : AIR FORCE RESEARCH LAB HANSCOM AFB MA SENSORS DIRECTORATE/ELECTROMAGNETICS TECHNOLOGY DIV


Personal Author(s) : Weyburne, David W.


Report Date : 14 SEP 2010


Pagination or Media Count : 20


Abstract : The problem of theoretically describing forced laminar flow over a flat plate is revisited. For the last hundred years it has been assumed that the Blasius solution model applies to this case. However, upon close review it is found that the Blasius model has a serious problem in that the Blasius model assumes that the pressure gradient on the plate in the flow direction is zero. In fact what one expects is that a pressure gradient develops as fluid is displaced from the plate due to the developing boundary layer. Therefore, the Blasius model is not a valid physical model of the flow over a flat plate as depicted in most textbooks. In this report, we develop a more realistic Falkner-Skan type similar solution that closely matches the flow one would expect for flow over a flat plate. We replace the usual zero pressure gradient assumption with a nonzero pressure gradient assumption. The resulting solution for the velocity profile parallel to the plate results in a velocity profile that is very similar to the Blasius solution velocity profile. The big difference in the two models is in the velocity perpendicular to the plate. For the Blasius solution, this velocity results in a net outflow whereas the new model's velocity results in a net inflow. This net inflow is critical in that it allows one to use the flat plate as a model for a wing with aerodynamic lift.


Descriptors :   *LAMINAR FLOW , *FLAT PLATE MODELS , AERODYNAMIC LIFT , BOUNDARY LAYER , PRESSURE GRADIENTS


Subject Categories : TEST FACILITIES, EQUIPMENT AND METEORS
      FLUID MECHANICS


Distribution Statement : APPROVED FOR PUBLIC RELEASE