Lateral jet injection into typical combustor flowfields

The trajectory, penetration and mixing efficiency of lateral air jet injection into typical combustor flowfields in the absence of combustion were investigated so as to characterize the time-mean and turbulence flowfield for a variety of configurations and input parameters, recommend appropriate turbulence model advances, and implement and exhibit results of flowfield predictions. A combined experimental and theoretical approach was followed, in a modified version of the test facility, equipped initially with one and two lateral jets, located one test-section downstream of the inlet

A note on the decay of aircraft trailing vortices

An elementary theory of aircraft trailing vortex decay is presented based on an assumed law for the variation of the mean eddy viscosity with distance from the wing. This law is based on the experimental data of Rose and Dee (1.963). The analysis gives results, as might be expected, in agreement with their data. The justification for the analysis must however be in doubt until more data are available covering a wide range of variables such as aircraft size, distance, incidence, etc

Turbulent Combustor Flowfield Investigation

The 2-D axisymmetric geometries under low speed, nonreacting, turbulent, swirling flow conditions were investigated. The effect of the parameters on isothermal flowfield patterns, time mean velocities and turbulence quantities is determined and an improved simulation in the form of a computer prediction code equipped with a suitable turbulence model is established. This is a prerequisite to the prediction of more complex turbulent reacting flows

Investigations of flowfields found in typical combustor geometries

Studies are concerned with experimental and theoretical research on 2-D axisymmetric geometries under low speed, nonreacting, turbulent, swirling flow conditions. The flow enters the test section and proceeds into a larger chamber (the linear expansion ratio D/d = 2, 1.5 and 1) via a sudden or gradual expansion (side wall angle alpha = 90 and 45 degrees). A weak or strong nozzle (of area ratio A/a = 2 and 4) may be positioned downstream at x/D = 2 to form a contraction exit to the test section. Inlet swirl vanes are adjustable to a variety of vane angles with values of theta = 0, 38, 45, 60 and 70 degrees being emphasized. The objective is to determine the effect of these parameters on isothermal flow field patterns, time mean velocities and turbulence quantities, and to establish an improved simulation in the form of a computer prediction code equipped with a suitable turbulence model. The goal of the on going research is to perform experiments and complementary computations with the idea of doing the necessary type of research that will yield improved calculation capability. This involves performing experiments where time mean turbulence quantities are measured and taking input conditions and running an existing prediction code for a variety of test cases so as to compare predictions against experiment

Predictions and measurements of isothermal flowfields in axisymmetric combustor geometries

Numerical predictions, flow visualization experiments and time-mean velocity measurements were obtained for six basic nonreacting flowfields (with inlet swirl vane angles of 0 (swirler removed), 45 and 70 degrees and sidewall expansion angles of 90 and 45 degrees) in an idealized axisymmetric combustor geometry. A flowfield prediction computer program was developed which solves appropriate finite difference equations including a conventional two equation k-epsilon eddy viscosity turbulence model. The wall functions employed were derived from previous swirling flow measurements, and the stairstep approximation was employed to represent the sloping wall at the inlet to the test chamber. Recirculation region boundaries have been sketched from the entire flow visualization photograph collection. Tufts, smoke, and neutrally buoyant helium filled soap bubbles were employed as flow tracers. A five hole pitot probe was utilized to measure the axial, radial, and swirl time mean velocity components

Confined turbulent swirling recirculating flow predictions

The capability and the accuracy of the STARPIC computer code in predicting confined turbulent swirling recirculating flows is presented. Inlet flow boundary conditions were demonstrated to be extremely important in simulating a flowfield via numerical calculations. The degree of swirl strength and expansion ratio have strong effects on the characteristics of swirling flow. In a nonswirling flow, a large corner recirculation zone exists in the flowfield with an expansion ratio greater than one. However, as the degree of inlet swirl increases, the size of this zone decreases and a central recirculation zone appears near the inlet. Generally, the size of the central zone increased with swirl strength and expansion ratio. Neither the standard k-epsilon turbulence mode nor its previous extensions show effective capability for predicting confined turbulent swirling recirculating flows. However, either reduced optimum values of three parameters in the mode or the empirical C sub mu formulation obtained via careful analysis of available turbulence measurements, can provide more acceptable accuracy in the prediction of these swirling flows

A simplified theory of skin friction and heat transfer for a compressible laminar boundary layer

The compressible laminar boundary layer equations for a perfect gas in steady flow at arbitrary external Mach number and wall temperature distribution are solved approximately by the combined use of the Stewartson- Illingworth transformation and application of Lighthill's method to yield the shin friction and rate of heat transfer. Appendices are added which give the necessary modifications to the method for the separate cases of very low Prandtl number and for the flow near a separation point. A further appendix describes Spalding's method for improving the accuracy of the wall value of shear stress and rate of heat transfer distributions along a wall having a non-uniform temperature distribution

On surface pressure fluctuations in turbulent boundary layers

Existing work on the pressure fluctuations in turbulent shear flaws is briefly reviewed with special reference to the problem of wall turbulence. An approximate theory for the pressure fluctuations on the wall under both a turbulent boundary layer and a wall jet is given and indicates in the latter case an intensity many times that corresponding to the flow over a flat plate at zero pressure gradient, as typified by measurements on the wall of a wind tunnel. Experiments on a wall jet confirm these predictions and details of the few preliminary data are presented. The results from the wall jet suggest that the intensity of the pressure fluctuations in the regions of adverse pressure gradient, on wings and bodies approaching and beyond separation will be higher than in regions of zero pressure gradient. Appendices are included which deal with the necessary extensions to the analysis to fit the velocity correlation functions as measured by Grant (1958), the effects of time delay and eddy convection

Wall pressure fluctuations under turbulent boundary layers at subsonic and supersonic speeds

The problem of pressure fluctuations at a rigid wall under a turbulent boundary layer has attracted much attention in the past decade. At low Mach numbers the theory is well established from the work of Kraichnan and Lilley, and reasonable agreement is obtained with the experiments of Willmarth, Hodgson and others. At high Mach numbers, measurements exist due to the work of Kistler and Chen but so far no theory is available, apart from that due to Phillips, which is however related to the noise radiated from supersonic turbulent shear flows. The present paper reviews the theory of wall pressure fluctuations in incompressible flow, and shows how the character of the pressure fluctuations changes in passing from the flow to the wall. Attention is drawn to the more important interactions giving rise to the pressure fluctuations, as well as to the region of the boundary layer mainly responsible for the wall pressure fluctuations … [cont.]

On surface pressure fluctuations in turbulent boundary layers

Existing work on the pressure fluctuations in turbulent shear flaws is briefly reviewed with special reference to the problem of wall turbulence. An approximate theory for the pressure fluctuations on the wall under both a turbulent boundary layer and a wall jet is given and indicates in the latter case an intensity many times that corresponding to the flow over a flat plate at zero pressure gradient, as typified by measurements on the wall of a wind tunnel. Experiments on a wall jet confirm these predictions and details of the few preliminary data are presented. The results from the wall jet suggest that the intensity of the pressure fluctuations in the regions of adverse pressure gradient, on wings and bodies approaching and beyond separation will be higher than in regions of zero pressure gradient. Appendices are included which deal with the necessary extensions to the analysis to fit the velocity correlation functions as measured by Grant (1958), the effects of time delay and eddy convection