The Flow Region Near the Nozzle in Double Concentric Jets

1964 ◽  
Vol 86 (4) ◽  
pp. 797-804 ◽  
Author(s):  
N. A. Chigier ◽  
J. M. Bee´r
Keyword(s):  
Static Pressure ◽  
Flow Region ◽  
Mean Velocity ◽  
Pressure Distributions ◽  
Air Jet ◽  
The Mean ◽  
Annular Jets ◽  
Made In

The type of double concentric jets considered in this paper consists of a central round air jet surrounded by an annular air jet issuing into stagnant air surroundings. Detailed measurements of the mean velocity and static-pressure distributions have been made in the region close to the exit of the nozzles and the effect of varying the ratio of the velocities in the central and annular jets has been examined.

scholarly journals Experimental Study of Twin Connected Pipe Jets

2020 ◽  
Vol 5 (12) ◽  
pp. 140-144
Author(s):  
Shams Sourav ◽  
Ashraful Hossain Rifat ◽  
Muhammed Hasnain Kabir Nayeem ◽  
Md. Abu Taher Ali
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Static Pressure ◽  
Recirculation Region ◽  
Central Plane ◽  
Mean Velocity ◽  
Air Jet ◽  
Velocity Flow ◽  
The Mean ◽  
Energy And Momentum

Two parallel pipe jets of 20 mm diameter were placed 1.2 mm diameter apart and were connected by a 4 mm wide channel all along the central plane of the jets. The mean velocity flow field of the jets was investigated for three Reynolds number 16300, 34400 and 49200. The Reynolds number was based on the exit velocity of the jets and jet diameter. The experiment was performed in an air jet facility and yaw meter was used for measurement of mean velocity and its direction. Their variations along the longitudinal, transverse, and lateral directions have been analyzed. A significant change of the jet flow field is observed near the exit of the jet. The combined effect of the jets diminishes the presence of recirculation region at the immediate exit rather enhances the energy and momentum transfer between their individual flow fields. Static pressure and kinetic energy distribution are also studied and a momentous variations have been noticed with varying Reynolds number.

The inner regions of annular jets

1979 ◽  
Vol 93 (3) ◽  
pp. 549-584 ◽  
Author(s):  
N. W. M. Ko ◽  
W. T. Chan
Keyword(s):  
Boundary Layer ◽  
Static Pressure ◽  
Outer Diameter ◽  
Mean Velocity ◽  
Wake Vortices ◽  
Annular Jet ◽  
Vortex Centre ◽  
The Mean ◽  
Inner Region ◽  
Annular Jets

Further experiments on the detailed study of annular jets are described in which the mean and fluctuating properties in the inner region have been measured. The experiments in the conical jetf have shown, besides the jet† vortices in the outer mixing region, another train of vortices in the inner region. This train of vortices is due to the wake formed by the boundary layer on the surface of the conical bullet.The experiments in the inner region of the basic annular jet have similar mean velocity profiles to those in the internal recirculating region. Good correlation is found for the location of the vortex centre, the location of reattachment, the minimum and maximum mean static pressure and their locations with the non-dimensional available pressure M°/AiPatm for entrainment behind the interface. A train of wake vortices is generated in the internal recirculating region and a train of jet vortices is found in the inner mixing region. Both types of vortices in the inner region seem to decay fairly rapidly within a distance of one outer diameter D° downstream.The disturbances associated with the wake vortices in the inner region seem to excite the outer mixing region. This results in another wave or train of vortices observed in the outer shear layer in addition to the jet vortices which are already in existence.

Velocity and Static-Pressure Distributions in Swirling Air Jets Issuing From Annular and Divergent Nozzles

1964 ◽  
Vol 86 (4) ◽  
pp. 788-796 ◽  
Author(s):  
N. A. Chigier ◽  
J. M. Bee´r
Keyword(s):  
Static Pressure ◽  
Reverse Flow ◽  
Ring Vortex ◽  
Pressure Gradients ◽  
Mean Velocity ◽  
Air Jets ◽  
Pressure Distributions ◽  
Angular Momenta ◽  
Set Up ◽  
Made In

Mean-velocity and static-pressure measurements have been made in a series of swirling air jets issuing from annular and divergent nozzles into stagnant-air surroundings. Swirl was generated by introducing varying proportions of air through tangential ports while the remainder of the air was introduced axially. A region of subatmospheric pressure is set up in the central region of the jets and as soon as the pressure gradients on the axis exceed a certain critical value, reverse flow is set up with an associated internal ring vortex. With increasing degrees of swirl, the angle of spread of the jets is increased and, correspondingly, the decay of the maximum values of axial, tangential, and radial components of velocity along the lengths of the jets is faster. The integrated axial fluxes of linear and angular momenta were shown to be conserved along the length of the jets.

Mean velocity and static pressure distributions of a circular jet

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 196-197
Author(s):  
M. T. Islam ◽  
M. A. T. Ali
Keyword(s):  
Static Pressure ◽  
Mean Velocity ◽  
Pressure Distributions

Static pressure distribution in the free turbulent jet

1957 ◽  
Vol 3 (1) ◽  
pp. 1-16 ◽  
Author(s):  
David R. Miller ◽  
Edward W. Comings
Keyword(s):  
Static Pressure ◽  
Longitudinal Velocity ◽  
Fluid Motion ◽  
Mean Velocity ◽  
Free Jet ◽  
Static Pressure Distribution ◽  
Two Dimensional Flow ◽  
The Common ◽  
Jet Theory ◽  
Made In

Measurements of mean velocity, turbulent stress and static pressure were made in the mixing region of a jet of air issuing from a slot nozzle into still air. The velocity was low and the two-dimensional flow was effectively incompressible. The results are examined in terms of the unsimplified equations of fluid motion, and comparisons are drawn with the common assumptions and simplifications of free jet theory. Appreciable deviations from isobaric conditions exist and the deviations are closely related to the local turbulent stresses. Negative static pressures were encountered everywhere in the mixing field except in the potential wedge region immediately adjacent to the nozzle. Lateral profiles of mean longitudinal velocity conformed closely to an error curve at all stations further than 7 slot widths from the nozzle mouth. An asymptotic approach to complete self-preservation of the flow was observed.

Prediction of Confined Coaxial Turbulent Jet Mixing With a Streamwise Differencing Scheme

1991 ◽  
Author(s):  
M. A. R. Sharif ◽  
M. A. Gadalla
Keyword(s):  
Reynolds Stresses ◽  
Low Velocity ◽  
Mean Velocity ◽  
Jet Mixing ◽  
Air Jet ◽  
Air Stream ◽  
Constant Diameter ◽  
Flow Domain ◽  
The Mean ◽  
Secondary Air

Abstract Isothermal turbulent mixing of an axisymmetric primary air jet with a low velocity annular secondary air stream inside a constant diameter cylindrical enclosure is predicted. The flow domain from the inlet to the fully developed downstream locations is considered. The predicted flow field properties include the mean velocity and pressure and the Reynolds stresses. Different velocity and diameter ratios between the primary and the secondary jets have been investigated to characterize the flow in terms of these parameters. A bounded stream-wise differencing scheme is used to minimize numerical diffusion and oscillation errors. Predictions are compared with available experimental data to back up numerical findings.

Heat Transfer in a Supersonic Parallel Diffuser

1965 ◽  
Vol 7 (1) ◽  
pp. 1-7 ◽  
Author(s):  
P. J. Baker
Keyword(s):  
Heat Transfer ◽  
Pressure Gradient ◽  
Cross Section ◽  
Static Pressure ◽  
Positive Pressure ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Flows ◽  
Pressure Distributions ◽  
The Mean

This paper presents the results of heat transfer measurements taken on a two-dimensional supersonic parallel diffuser. The wall static pressure distributions and the corresponding heat transfer coefficients and fluxes have been measured for a range of initial total pressures. The effects of varying the area of the diffuser cross-section for the same upstream generating nozzle have also been studied. Mach number profiles measured at sections along the diffuser show that in the presence of shock waves and a positive pressure gradient the flow is very much underdeveloped. In general, the mean level of heat transfer is found to be much greater than that predicted by conventional empirical equations for subsonic pipe flows with zero pressure gradient. Further, on comparison between normal and oblique shock diffusion the former is found to give the higher level of heat transfer.

Establishment of the Wake Behind a Disk

1964 ◽  
Vol 86 (4) ◽  
pp. 869-880 ◽  
Author(s):  
Thomas Carmody
Keyword(s):  
Shear Stress ◽  
Ambient Pressure ◽  
Continuous Distribution ◽  
Flow Characteristics ◽  
Graphical Form ◽  
Stress Distributions ◽  
Mean Velocity ◽  
Pressure Distributions ◽  
Energy Relationships ◽  
The Mean

An air-tunnel study of the establishment of the wake behind a disk at a Reynolds number of approximately 7 × 104 was undertaken. On the basis of the measured data, such a wake is fully established, that is, similarity profiles of the flow characteristics are formed, within 15 diameters of the disk, and approximately 95 percent of the transfer of energy from the mean motion to the turbulence motion takes place within 3 diameters of the disk, in the region of the mean standing eddy. The measured mean ambient-pressure and mean total-pressure distributions, mean velocity distributions, turbulence-intensity and shear-stress distributions, and the mean streamline pattern are presented in graphical form, as are the quantitative balances of the integrated momentum and mean-energy relationships. A stream function consisting of a continuous distribution of doublets is introduced to extend the radial limit of understanding of the flow characteristics to a very large if not infinite radius. Considerable attention is given to the problem of obtaining and interpreting turbulence shear-stress data immediately downstream from the point of flow separation. The applicability of a local diffusion coefficient or virtual viscosity of the Boussinesq or Prandtl type for relating the turbulence shear stress to the radial gradient of mean axial velocity is discussed. The Bernoulli sum and the energy changes along individual streamlines investigated in an associated study are incorporated herein to obtain a quantitative estimate of the local errors involved in the turbulence-shear-stress measurements.

Turbulence measurements in axisymmetric jets of air and helium. Part 2. Helium jet

1993 ◽  
Vol 246 ◽  
pp. 225-247 ◽  
Author(s):  
N. R. Panchapakesan ◽  
J. L. Lumley
Keyword(s):  
Density Ratio ◽  
Effective Diameter ◽  
Mean Velocity ◽  
Velocity Fluctuations ◽  
Air Jet ◽  
Plume Region ◽  
Turbulent Schmidt Number ◽  
Radial Profiles ◽  
The Mean ◽  
Mean Concentration

A turbulent round jet of helium was studied experimentally using a composite probe consisting of an interference probe of the Way–Libby type and an × -probe. Simultaneous measurements of two velocity components and helium mass fraction concentration were made in the x/d range 50–120. These measurements are compared with measurements in an air jet of the same momentum flux reported in Part 1. The jet discharge Froude number was 14000 and the measurement range was in the intermediate region between the non-buoyant jet region and the plume region. The measurements are consistent with earlier studies on helium jets. The mass flux of helium across the jet is within ±10% of the nozzle input. The mean velocity field along the axis of the jet is consistent with the scaling expressed by the effective diameter but the mean concentration decay constant exhibits a density-ratio dependence. The radial profiles of mean velocity and mean concentration agree with earlier measurements, with the half-widths indicating a turbulent Schmidt number of 0.7. Significantly higher intensities of axial velocity fluctuations are observed in comparison with the air jet, while the intensities of radial and azimuthal velocity fluctuations are virtually identical with the air jet when scaled with the half-widths. Approximate budgets for the turbulent kinetic energy, scalar variance and scalar fluxes are presented. The ratio of mechanical to scalar timescales is found to be close to 1.5 across most of the jet. Current models for triple moments involving scalar fluctuations are compared with measurements. As was observed with the velocity triple moments in Part 1, the performance of the Full model that includes all terms except advection was found to be very good in the fully turbulent region of the jet.

Pressure-Probe Interference in a Vortex Flow

1978 ◽  
Vol 5 (2) ◽  
pp. 106-110
Author(s):  
O.O. Mojola
Keyword(s):  
Vortex Flow ◽  
Static Pressure ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Flow Region ◽  
Pressure Probe ◽  
Pressure Data ◽  
Pressure Sensing ◽  
Recirculation Flow ◽  
Made In

This paper examines the sensitivity of vortex-flows to disturbances arising from the insertion of conventional pressure-sensing probes into the flows. With a wide variety of pitot-tubes, static-pressure probes, and transverse-cylinder yawmeters, measurements were made in the vortex (recirculation) flow region of a separated, three-dimensional, turbulent boundary layer upstream of a vertical wall. The measurements, which included both local and surface pressure data, have been analysed to reveal how the shape, size, and alignment of probes independently and collectively contribute to the probe interference.

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