Radial Jet Flow Research Articles

A Novel Experiment to Understand the Dynamic Stall Phenomenon in Rotor Axial Flight

A rotor test facility was developed to investigate dynamic stall under optimized boundary conditions compared to conventional hover chambers. lt features a defined axial inflow, reduction of ground effect and recirculation of the rotor wake and good optical access to apply non-intrusive measuring techniques. The rotor consists of two blades with an aspect ratio of 6.8 and a tip radius of 0.65m. lt was operated at a Mach number of 0.21 and a chord based Reynolds number of 350000, both at 75% radius. The flow and blade deformation were analyzed by means of unsteady blade pressure transducers, particle image velocimetry and tip deflection measurements covering the whole azimuth and different radii. Three measurement approaches to detect flow separation: tufts, differential infrared thermography and surface pressure analysis showed comparable results and flow separation over one half of the cycle. A radiusdependent separation point in time and an altering of the dynamic stall behavior near the tip were observed. The recirculation area remained close to the blade's surface with radial jet flow increasing towards the tip. A maximum increase of the effective angle of attack of 1.4° was observed due to blade deformation. For a fully attached flow case the laminar-turbulent boundary layer transition differed along the radius and moved over 70% of the blade's chord.

Conservation Laws and Nonlocally Related Systems of Two-Dimensional Boundary Layer Models

Abstract Local conservation laws, potential systems, and nonlocal conservation laws are systematically computed for three-equilibrium two-component boundary layer models that describe different physical situations: a plate flow, a flow parallel to the axis of a circular cylinder, and a radial jet striking a planar wall. First, local conservation laws of each model are computed using the direct method. For each of the three boundary layer models, two local conservation laws are found. The corresponding potential variables are introduced, and nonlocally related potential systems and subsystems are formed. Then nonlocal conservation laws are sought, arising as local conservation laws of nonlocally related systems. For each of the three physical models, similar nonlocal conservation laws arise. Further nonlocal variables that lead to further potential systems are considered. Trees of nonlocally related systems are constructed; their structure coincides for all three models. The three boundary layer models considered in this work provide rich and interesting examples of the construction of trees of nonlocally related systems. In particular, the trees involve spectral potential systems depending on a parameter; these spectral potential systems lead to nonlocal conservation laws. Moreover, potential variables that are not locally related on solution sets of some potential systems become local functions of each other on solution sets of other systems. The point symmetry analysis shows that the plate and radial jet flow models possess infinite-dimensional Lie algebras of point symmetries, whereas the Lie algebra of point symmetries for the cylinder flow model is three-dimensional. The computation of nonlocal symmetries reveals none that arise for the original model equations, which is common for partial differential equations (PDE) systems without constitutive parameters or functions, but does reveal nonlocal symmetries for some nonlocally related PDE systems.

Radial Jet Reattaching on a Rotating Disk

This study is concerned with the characteristics of a radial jet flow which reattaches on a coaxially rotating disk that the disk sets parallel to a cylindrical nozzle. The velocity fields near the disk surface and in the jet were measured by a hot-wire probe to clarify the variation of the basic characteristics of the flow. As the offset distance from the wall to the nozzle (step height) becomes high, the reattachment position moves to the upstream side depending on the disk rotating speed. The basic characteristics of the jet until it reattaches on the disk are similar to the radial free jet. In contrast, after the reattachment, they show the change similar to the radial wall jet without step height. Furthermore, the velocity in the reattaching region fluctuates periodically, and the frequency of the fluctuation decreases with the step height and increases with the disk rotating speed.

1902 回転する側壁平板に再付着する放射状噴流(S21-1 噴流,後流及びはく離流れの流動解析と応用(1),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

This study is concerned with the characteristics of the radial jet flow which reattaches on a rotating disk. The velocity fields near the side wall and in the jet were measured to clarify the variation of the basic characteristics of the mean flow. As the step height becomes high, the reattachment position of the jet moves to the upstream side depending on the increase of the disk rotating speed. The maximum velocity and the jet half-width change like the radial free jet until reattaching on a disk, and they show the change similar to the radial wall jet after the reattachment.

Flow Generated by an Aerated Rushton Impeller: Two‐phase PIV Experiments and Numerical Simulations

AbstractA two‐camera PIV technique was used to obtain angle resolved velocity and turbulence data of the flow in a lab‐scale stirred tank, equipped with a Rushton turbine. Two cases were investigated: a single‐phase flow and a gas‐liquid flow. In the former case, the classical radial jet flow pattern accompanied by two trailing vortices was observed. In the latter case, the velocity of the radial jet was reduced, and the vortices were diminished by the presence of the gas. Gas cavities clinging to the back of the impeller blades were observed. Both cases were also investigated with the use of three‐dimensional transient CFD simulations. For the single‐phase flow the simulations in the impeller region correspond very well with the experimental data. For the gas‐liquid flow both the mean and fluctuating liquid velocities in the impeller region are well predicted. This is also the case for the mean radial gas velocities.

LONG RANGE EXHAUSTION—A MATHEMATICAL MODEL FOR THE AXISYMMETRIC AIR FLOW OF A LOCAL EXHAUST VENTILATION HOOD ASSISTED BY A TURBULENT RADIAL JET

Abstract Mathematical modelling techniques are used to predict the axisymmetric air flow pattern developed by a state-of-the-art flanged exhaust hood which is reinforced by a turbulent radial jet flow. The high Reynolds number modelling techniques adopted allow the complexity of determining the hood's air flow to be reduced and provide a means of identifying and assessing the various parameters that control the air flow. The mathematical model is formulated in terms of the Stokes steam function, Ψ, and the governing equations of fluid motion are solved using finite-difference techniques. The injection flow of the exhaust hood is modelled as a turbulent radial jet and the entrained flow is assumed to be an inviscid potential flow. Comparisons made between contours of constant air speed and centre-line air speeds deduced from the model and all the available experimental data show good agreement over a wide range of typical operating conditions.

Long range exhaustion—A mathematical model for the axisymmetric air flow of a local exhaust ventilation hood assisted by a turbulent radial jet

Mathematical modelling techniques are used to predict the axisymmetric air flow pattern developed by a state-of-the-art flanged exhaust hood which is reinforced by a turbulent radial jet flow. The high Reynolds number modelling techniques adopted allow the complexity of determining the hood's air flow to be reduced and provide a means of identifying and assessing the various parameters that control the air flow. The mathematical model is formulated in terms of the Stokes steam function, Ψ, and the governing equations of fluid motion are solved using finite-difference techniques. The injection flow of the exhaust hood is modelled as a turbulent radial jet and the entrained flow is assumed to be an inviscid potential flow. Comparisons made between contours of constant air speed and centre-line air speeds deduced from the model and all the available experimental data show good agreement over a wide range of typical operating conditions.

03 O 03 A 3-dimensional axisymmetric model of the air flow pattern created by a local exhaust ventilation system reinforced by a turbulent radial jet flow

03 O 03 A 3-dimensional axisymmetric model of the air flow pattern created by a local exhaust ventilation system reinforced by a turbulent radial jet flow

Experimental Studies of a Radial Turbulent Jet : 5th Report, Attaching Jet Flow from an Inclined Nozzle on an Adjacent Offset Disc Plate

A study has been made of the attachment of a radial jet flow discharged from an inclined nozzle on an adjacent offset disc plate. Mean velocity, turbulent velocity and static pressure distributions were measured. The effects of the angle of inclined nozzle to the disc plate, and also of the distance of nozzle center from the offset plate on flow pattern were investigated. Length and average negative pressure in the region of recirculating flow were examined. The results were compared with those obtained for a two-dimensional attaching jet flow to an inclined flat plate. Changes of maximum jet center velocity and jet half width of the flows before and after an attaching point along the flow were measured, and the results were compared with those obtained for a radial free jet flow or a radial wall jet flow, respectively.

Measurements of Mean Flow Velocity Beyond a Rotating Disk

Measurements were made of the mean velocity components of the turbulent flow field just beyond the edge of a thin disk rotating in its own plane. An approximate analysis was made of the turbulent strongly swirling radial jet flow region by recourse to the momentum integral technique. Comparison with experiment indicated that approximate similarity of both the tangential and radial velocity components was achieved in a few disk thicknesses. The angle of the flow from radial in the disk plane compared fairly well with that predicted by the present analysis but poorly with the exact asymptotic theory. Nearly discrete frequency vortex shedding at the disk edge was detected by pressure-correlation measurements just outside the boundary layer.

Underexpanded jet noise reduction using radial flow impingement.

Reduction of noise from underexpanded axisymmetric jet flows using radial jet flow impingement