The main objective of this study is to determine the effect of vortex generators on a friction factor for fully developed flow of a fluid such as air. Longitudinal vortices can be generated in a channel flow by punching or mounting protrusions in the channel wall. Such vortex generators (VGs) can be classified into delta wing, rectangular wing, pair of delta-winglet and pair of rectangular winglet. These longitudinal vortices disrupt the growth of the boundary layer and lead to enhance the heat transfer rate between the working fluid and the conductor channel wall, but this enhancement is associated with increasing in a pressure gradient along the axial length of the channel. So, the friction factor for fully developed air flow in an equilateral triangular duct is investigated experimentally with Reynolds number ranging from (31,000) to (53,000) and the size of the generators was kept constant for three cases which are single, double, and triple pairs of delta–winglet type of vortex generators embedded in the turbulent boundary layer for attack angle of generator of (30, 40, and 50 ) degree. The results show that the friction factor increases by about (43.5 %) when the angle of attack is varied from (30 deg) to (50 deg) for the triple pairs case compared with the base case (without VG).
An experimental investigation is performed to study the friction factor ( f ) and convection heat transfer coefficient (h) behavior in an asymmetrically heated equilateral triangular duct by using delta–winglets vortex generators which are embedded in a turbulent boundary layer. Two side walls of the heated test section are electrically heated with a constant heat flux, whereas the lower wall is indirectly heated. Reynolds number (Re) is ranged from (23,000) to (58,000). Two sizes and three attack angles of vortex generators are studied here for three cases; single, double, and treble pairs of generators. Each pair was supported in one wall of the test section at the various locations from the leading edge. The indicated results that friction factor ( f )and Nusselt number (Nu) are relatively proportion with the size, number and the inclination angle of the generators. The ( f ) decreases as airflow rate increases whereas Nu number increases. The present data of ( f ) is less than the data of Chegini by about (6.5 %) and overpredicts the data of Altemani by about (1.7 %).
The Cooper-Harper rating of aircraft handling qualities has been adopted as a standard for measuring the performance of aircraft. In the present work, the tail plane design for satisfying longitudinal handling qualities has been investigated with different tail design for two flight conditions based on the Shomber and Gertsen method. Tail plane design is considered as the tail/wing area ratio. Parameters most affecting on the aircraft stability derivative is the tail/wing area ratio. The longitudinal handling qualities criteria were introduced in the mathematical contributions of stability derivative. This design technique has been applied to the Paris Jet; MS 760 Morane-Sualnier aircraft. The results show that when the tail/wing area ratio increases the aircraft stability derivative increases, the damping ratio and the natural frequency increases and the aircraft stability is improved. Three regions of flight conditions had been presented which are satisfactory, acceptable and unacceptable. The optimum tail/wing area ratio satisfying the longitudinal handling qualities and stability is (0.025KeywordsLongitudinal Handling---Stability---Tail Design