A calculation of the suction requirements to prevent boundary layer separation on a circular cyclinder

An investigation was made to test the method of Head on the flow about a circular cylinder with suction. The method of Head is an approximate method of obtaining solutions to the boundary layer equations. The method was adapted to the digital computer to facilitate performing the calculations, and a variety of suction distributions were studied. In the cases where an exact solution of the boundary layer equations was available the results were compared. The method predicted a point of separation comparable to exact solutions for the case in which the suction velocity was zero. However, for the large suction velocities and large adverse pressure gradients associated with the circular cylinder, the method broke down. Enough information was obtained before breakdown to indicate that another approximate method due to Ando underestimates the suction required to prevent separation

Cooling Air Inlet and Exit Geometries on Aircraft Engine Installations

A semispan wing and nacelle of a typical general aviation twin-engine aircraft was tested to evaluate the cooling capability and drag or several nacelle shapes; the nacelle shapes included cooling air inlet and exit variations. The tests were conducted in the Ames Research Center 40 x 80-ft Wind Tunnel. It was found that the cooling air inlet geometry of opposed piston engine installations has a major effect on inlet pressure recovery, but only a minor effect on drag. Exit location showed large effect on drag, especially for those locations on the sides of the nacelle where the suction characteristics were based on interaction with the wing surface pressures

Suckdown, fountain lift, and pressures induced on several tandem jet V/STOL configurations

As part of a program to improve the methods for predicting the suckdown and hot gas ingestion for jet V/STOL aircraft in ground effect, a data base is being created that provides a systematic variation of parameters so that a new empirical prediction procedure can be developed. The first series of tests in this program was completed. Suckdown, fountain lift, and pressures induced on several two-jet V/STOL configurations are described. It is one of three reports that present the data obtained from tests conducted at Lockheed Aeronautical Systems-Rye Canyon Facility and in the High Bay area of the 40 by 80 foot wind tunnel complex at NASA Ames Research Center

Effect of Propeller on Engine Cooling System Drag and Performance

The pressure recovery of incoming cooling air and the drag associated with engine cooling of a typical general aviation twin-engine aircraft was Investigated experimentally. The semispan model was mounted vertically in the 40 x 80-Foot Wind Tunnel at Ames Research Center. The propeller was driven by an electric motor to provide thrust with low vibration levels for the cold-now configuration. It was found that the propeller slip-stream reduces the frontal air spillage around the blunt nacelle shape. Consequently, this slip-stream effect promotes flow reattachment at the rear section of the engine nacelle and improves inlet pressure recovery. These effects are most pronounced at high angles of attack; that is, climb condition. For the cruise condition those improvements were more moderate

Forces and pressures induced on circular plates by a single lifting jet in ground effect

NASA Ames is conducting a program to develop improved methods for predicting suckdown and hot-gas ingestion on jet V/STOL aircraft when they are in ground effect. As part of that program a data base is being created that provides a systematic variation of parameters so that current empirical prediction procedures can be modified. The first series of tests in this program is complete. This report is one of three that presents the data obtained from tests conducted at Lockheed Aeronautical Systems - Rye Canyon Facility and the High Bay area of the 40 by 80 foot Wind Tunnel at Ames Research Center. Suckdown on two circular plates is examined

Full-Scale Wind-Tunnel Study of the Effect of Nacelle Shape on Cooling Drag

Tests were made in the Ames 40 by 80 ft Wind Tunnel of a semispan wing with a nacelle (no propeller) from a typical, general aviation twin-engine aircraft. Measurements were made of the effect on drag of the flow of cooling air through the nacelle. Internal and external nacelle pressures were measured. It was found that the cooling airflow accounts for about 13% of the total estimated airplane drag during both cruise and climb. The now of cooling air through the nacelle accounts for 30% of the airflow drag component during cruise and 42% during climb; the balance, in both cruise and climb, is attributed to [he external shape of the nacelle. It was suggested that improvements could possibly be made by relocating both the inlet and the outlet for the cooling air

On the estimation of jet-induced fountain lift and additional suckdown in hover for two-jet configurations

Currently available methods for estimating the net suckdown induced on jet V/STOL aircraft hovering in ground effect are based on a correlation of available force data and are, therefore, limited to configurations similar to those in the data base. Experience with some of these configurations has shown that both the fountain lift and additional suckdown are overestimated but these effects cancel each other for configurations within the data base. For other configurations, these effects may not cancel and the net suckdown could be grossly overestimated or underestimated. Also, present methods do not include the prediction of the pitching moments associated with the suckdown induced in ground effect. An attempt to develop a more logically based method for estimating the fountain lift and suckdown based on the jet-induced pressures is initiated. The analysis is based primarily on the data from a related family of three two-jet configurations (all using the same jet spacing) and limited data from two other two-jet configurations. The current status of the method, which includes expressions for estimating the maximum pressure induced in the fountain regions, and the sizes of the fountain and suckdown regions is presented. Correlating factors are developed to be used with these areas and pressures to estimate the fountain lift, the suckdown, and the related pitching moment increments