Shigeo Hayashibara

Effect of Canards on Delta Wing Vortex Breakdown During Dynamic Pitching

The effect of a canard on delta wing vortices was investigated in the 2 3 3 ft water tunnel at Wichita State University. It is well known that the leading-edge vortices generated by a delta-shaped wing greatly enhance a vehicle’ s performance at high angles of attack. In this experiment, different canards were placed in front of a 70-deg swept main delta wing. Dye e ow visualization was used to observe the vortex breakdown location during dynamic pitch-up and pitch-down motion with varying pitch rates. Compared to the no-canard cone guration, results showed that there was a delay in vortex breakdown because of the presence of the canard and the dynamic pitch motion. The most favorable delay was obtained when the canard was located closest to the main delta wing and the model was pitched up at a fast rate or pitched down at a slow rate. Complete vortex breakdown on the main delta wing (i.e., full stall ) occurred at 53 deg for the static case without canard. In comparison, complete vortex breakdown occurred past 90 deg when a canard cone gured delta wing was pitched up at the fastest rate tested (i.e., k = 0.2).

Diamond, Cropped, Delta, and Double-Delta Wing Vortex Breakdown During Dynamic Pitching

A series of experiments were conducted on the effect of different delta wing shapes on vortex breakdown under dynamic pitching conditions.

Flow Visualization Study on the Effect of a Gurney Flap in a Low Reynolds Number Compressor Cascade

The effect of a Gurney flap in a compressor cascade model at low Reynolds number was investigated using tuft flow visualization in a water table facility. Although small in scale, water tables have the advantage of low cost and the ease with which test conditions can be varied. In this experiment, tuft flow visualization was used to determine the outgoing flow angle for a NACA 65-(12)10 compressor cascade model with a solidity of 1.5 at a blade chord Reynolds number of 16,000. The baseline (no flap) results were found to be in good agreement compared to results in the literature for tests conducted at Reynolds number in the 250,000 + range. A second set of measurements were then taken for a Gurney flap with a height of 2% of the chord length attached to the trailing edge of the cascade blades. The results suggest that the Gurney flap energizes the flow and delays the stall at large incoming flow angles. Nomenclature c = chord length Re C = Reynolds number based on chord length, Uc/ν U = freestream velocity y = offset distance in the stagger direction βin = incoming flow angle, between the in-flow direction and a line perpendicular to the stagger line βout = outgoing flow angle, between the out-flow direction and a line perpendicular to the stagger line λ = stagger angle, between the chord line and a line perpendicular to the stagger line ν = kinematic viscosity σ = solidity of cascade, c/y

The effect of a 70 deg swept canard on the leading-edge vortices of a 70 deg swept delta wing during dynamic pitching

The effect of a canard on delta wing vortices was investigated in the 2 ft x 3 ft water tunnel at Wichita State University. It is well known that the leading-edge vortices generated by a delta-shaped wing greatly enhance a vehicles performance at high angles of attack. In this experiment, a 70 swept canard was placed in front of a 70 deg swept main delta wing. Dye flow visualization was used to observe the vortex breakdown location during dynamic pitch-up and pitch-down motion with varying pitch rates. Compared to the no canard configuration, results showed that there was a delay in vortex breakdown due to the presence of the canard and the dynamic pitch motion. The most favorable delay was obtained when the canard was located closest to the main delta wing and the model was pitched up at a fast rate or pitched down at a slow rate. Complete vortex breakdown on the main delta wing occurred at 53 deg for the static case without canard. In comparison, complete vortex breakdown did not occur until 90 deg when the canard configured delta wing was pitched up at a very fast rate. (Author)

Comparison of Theoretical and Semi-Empirical Solutions for Dissipation Coefficient in a Low Reynolds Number Compressor Cascade

A comparison was made between the theoretical and semi-empirical solutions of the dissipation coefficient in a low Reynolds number NACA 65-series compressor cascade. The entropy generation rate quantifies the energy dissipated within the boundary layer, and this quantity can be transformed into a non-dimensional form known as the dissipation coefficient. The dissipation coefficient was determined from blade surface laminar boundary layer measurements at a chord Reynolds number of 8,500 and solidities of 1.5 and 2.0 at a fixed inflow angle of 40/. Results show that the semi-empirical method is able to predict the dissipation coefficient in good agreement with the theoretical results. This suggests that the semi-empirical method may be used as an alternative method for determining the entropy generation rate, and provide a tool in the design of compressor cascade blades and their optimization.

Effect of Stagger Angle on the Generation of Entropy in a Low Reynolds Number Compressor Cascade

The entropy generated in a compressor cascade at low Reynolds number was determined from the blade surface boundary layer measurements. Accurately predicting the turbomachinery stage efficiency is one of the more challenging p roblems in prop ulsion d ue t o the complexity of the f low field. R ather than conduct turbomachinery tests under full scale high temperature rotating flow conditions, a better understanding of some of the root causes of loss, in the form of entropy generated, might be obtained through two-dimensional cascade measurements. An experimental and computational study was conducted to determine the entropy generation rate based on boundary layer profiles for a NACA 65-series compressor cascade model at a chord Reynolds number of 8,500. For moderate solidity of 1.5 and fixed inflow angle of 40°, results show that the amount of entropy generated increases with increasing stagger angle. Nomenclature c = chord length (m) p c = specific heat at constant pressure (J/kg/K) p h = enthalpy, c T (J/kg) P = pressure (N/m ) 2 R = gas constant (J/K/kg) C Re = Reynolds number based on chord length, Uc/ν where U is the freestream velocity s = entropy per unit mass [lower case s] (J/K/kg) = entropy [upper case S] generation rate [dot] (W/K) = entropy [upper case S] generation rate [dot] per unit span [prime] (W/K/m) = entropy [upper case S] generation rate [dot] per unit area [double-prime] (W/K/m ) 2

Determining the Entropy Generated in a Low Reynolds Number Compressor Cascade Based on the Wake Velocity Profile

= chord length (m) p c = specific heat at constant pressure (J/kg/K) p h = enthalpy, c T (J/kg) P = pressure (N/m ) 2 R = gas constant (J/K/kg) C Re = Reynolds number based on chord length, Uc/ν where U is the freestream velocity s = entropy per unit mass (lower case s) (J/K/kg) = entropy (upper case S) generation rate (dot) (W/K) = entropy (upper case S) generation rate (dot) per unit span (prime) (W/K/m) = entropy (upper case S) generation rate (dot) per unit area (double-prime) (W/K/m ) 2