Experimental Study of Submerged Turbulent Twin Jets Interacting with a Free Surface and a Solid Wall PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Experimental Study of Submerged Turbulent Twin Jets Interacting with a Free Surface and a Solid Wall PDF full book. Access full book title Experimental Study of Submerged Turbulent Twin Jets Interacting with a Free Surface and a Solid Wall by Ebenezer Essel. Download full books in PDF and EPUB format.
Author: Ebenezer Essel
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
This thesis presents an experimental investigation of the effects of offset height ratio and boundary condition (free surface and solid wall) on the turbulence characteristics of submerged twin jets issuing from two parallel round nozzles. A particle image velocimetry (PIV) technique was used to conduct two sets of experiments. The first set of experiments focused on twin surface jets at Reynolds number, Re = 4400, separation ratio (G/d = 2.3) and offset heights, 1d, 2d, 3d and 4d from the free surface. The second set of experiments, which was designed based on the main findings of the previous experiment, examined the effects of free surface and wall on the turbulence structure of the twin jets. These experiments were performed at Re = 5000, G/d = 2 and offset heights, 1d, 2d and 4d from the free surface or wall. For the surface jets, the mean velocity and turbulence intensities at the free surface rapidly increased beyond the attachment point by amounts that increases with decreasing offset ratio. Further downstream, the surface transverse turbulence intensities decayed to negligible values while the streamwise turbulence intensities were persistent because of the energy redistribution from the transverse Reynolds normal stress to the tangential (streamwise and spanwise) Reynolds stresses. For both boundary conditions, the attachment length, Reynolds stresses and the spatial extents of the large-scale structures increased with increasing offset ratio. The transition of the twin jets to a single jet was more rapid as offset ratio increases due to the enhanced entrainment and mixing for larger offset ratios. The evolution of the jet farther away from the free surface or wall behaved like a free jet, but the decay rate of the jet interacting with each boundary was substantially reduced in the far field due to confinement effects. The difference between the effects of free surface and wall on the mean velocity, Reynolds stresses and triple velocity correlations were confined to the immediate vicinity of each boundary. The interaction between the large-scale structures and the boundaries were also investigated using various multi-point statistical techniques such as discrete wavelet transform, linear stochastic estimation, swirling strength, joint probability density function and two-point velocity correlations. The results showed that, the wall considerably reduced the spatial coherence of the structures embodied in the transverse auto-correlations compared to those near the free surface.
Author: Ebenezer Essel
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
This thesis presents an experimental investigation of the effects of offset height ratio and boundary condition (free surface and solid wall) on the turbulence characteristics of submerged twin jets issuing from two parallel round nozzles. A particle image velocimetry (PIV) technique was used to conduct two sets of experiments. The first set of experiments focused on twin surface jets at Reynolds number, Re = 4400, separation ratio (G/d = 2.3) and offset heights, 1d, 2d, 3d and 4d from the free surface. The second set of experiments, which was designed based on the main findings of the previous experiment, examined the effects of free surface and wall on the turbulence structure of the twin jets. These experiments were performed at Re = 5000, G/d = 2 and offset heights, 1d, 2d and 4d from the free surface or wall. For the surface jets, the mean velocity and turbulence intensities at the free surface rapidly increased beyond the attachment point by amounts that increases with decreasing offset ratio. Further downstream, the surface transverse turbulence intensities decayed to negligible values while the streamwise turbulence intensities were persistent because of the energy redistribution from the transverse Reynolds normal stress to the tangential (streamwise and spanwise) Reynolds stresses. For both boundary conditions, the attachment length, Reynolds stresses and the spatial extents of the large-scale structures increased with increasing offset ratio. The transition of the twin jets to a single jet was more rapid as offset ratio increases due to the enhanced entrainment and mixing for larger offset ratios. The evolution of the jet farther away from the free surface or wall behaved like a free jet, but the decay rate of the jet interacting with each boundary was substantially reduced in the far field due to confinement effects. The difference between the effects of free surface and wall on the mean velocity, Reynolds stresses and triple velocity correlations were confined to the immediate vicinity of each boundary. The interaction between the large-scale structures and the boundaries were also investigated using various multi-point statistical techniques such as discrete wavelet transform, linear stochastic estimation, swirling strength, joint probability density function and two-point velocity correlations. The results showed that, the wall considerably reduced the spatial coherence of the structures embodied in the transverse auto-correlations compared to those near the free surface.
Author: Chidiebere Felix Nwaiwu
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
The effects of nozzle geometry on the mean and turbulent characteristics of submerged twin jets were experimentally investigated. The experiments were conducted at fixed Reynolds number and offset height ratio of 4,400 and h⁄d=2, respectively. The jets were produced from three nozzle geometries: round, square, and rectangle, with the rectangular nozzle geometry oriented in the minor (rect_min) and major (rect_maj) planes. The twin nozzles of each geometry type were aligned parallel to the free surface, and the separation ratio between the twin jets was fixed at G⁄d=2.3 for all cases. Velocity measurements were obtained using a particle image velocimetry (PIV) technique, and analyses of various quantities such as the instantaneous, mean, and surface velocities, as well as the turbulent statistics were performed. The jet-free surface interaction was examined using mean and turbulent surface velocities at the free surface, velocity defect, and vorticity thickness. Two-point velocity correlation and joint probability density function revealed the dynamics of the turbulent structures. Results from the velocity contours showed that the shear layer expansion was most rapid in twin jets produced from the rect_min nozzle geometry, which resulted in the shortest attachment length to the free surface. The instantaneous velocity field showed the most prograde and retrograde vortices in the rect_min nozzle geometry, accounting for the fastest shear layer expansion. Surface-normal profiles of the Reynolds stress ratio showed an enhancement of about 60% at the free surface and that the Townsend structure parameter was dependent on nozzle geometry. The mean surface velocity revealed that the free surface was in a state of strain due to alternating velocity gradient and was most intense in the rect_min jet. Large-scale structures produced along the centreline of the jet father away from the free surface (jet B) showed a larger streamwise extent compared to those along the centreline of the jet closer to the free surface (jet A) and were independent of nozzle geometry. Analysis of the joint probability density function of the streamwise and surface-normal velocity fluctuations showed that within the shear layer, the Reynolds shear stress producing events were dominated by slow entrainment and fast ejection events, and the damping effect of the free surface was least on the rect_min jets.
Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 400
Get Book Here
Book Description
Author: Norberto Mangiavacchi
Publisher:
ISBN:
Category :
Languages : en
Pages : 320
Get Book Here
Book Description
Author: Christos D. Tsitouras
Publisher:
ISBN:
Category : Air jets
Languages : en
Pages : 402
Get Book Here
Book Description
Author: G. N. Abramovich
Publisher: Mit Press
ISBN: 9780262511377
Category : Technology & Engineering
Languages : en
Pages : 671
Get Book Here
Book Description
The author's first monograph on turbulent jets, in 1936, dealt solely with a free submerged jet. Since that time, the theory of the turbulent jet has been developed in many published works both in the USSR and abroad: it has been enriched with a large amount of experimental material and has been applied in many new fields of engineering. In the last 10 years very substantial progress has been made, and it has now become possible to go beyond the free submerged jet and to solve the problem of a jet in a stream of fluid, to take into account the interaction between the jet and solid walls, to ascertain the relationship between the contour of the jet and the ratio of its density to the density of the surrounding medium, and to establish the characteristic features of a supersonic jet. This monograph contains the results of further research by the author and his colleagues, as well as a critical reappraisal of the more important theoretical and experimental data published by other investigators. The first section deals with the theory of a turbulent jet of incompressible fluid. It gives a systematic analysis of numerous experimental data on velocity profiles, temperature, and the impurity concentration, as well as the outlines of the turbulent mixing lone. The second section sets forth the theory of turbulent gas jets, including strongly preheated and supersonic jets. The theory of free turbulence in a gas, suitable in principle for any degree of compressibility, is revised, and the equations are derived for motion and heat exchange in the boundary layer of a jet at very high temperature. The third section solves several problems of the spreading of jets in finite and semifinite space, and the fourth section describes various applications of the theory of jets, many of which are reported for the first time or have been significantly revised.
Author: Duygu Erdem
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Interaction of two incompressible rectangular jets and impingement of twin jets on a flat surface are investigated experimentally in the present study. Five different twin jet geometries are used to perform the measurements.Detailed analysis of initial flow characteristics as the initial boundary layer,turbulence level and the initial spectral distribution of the velocity fluctuations are presented first. Twin jet flow characteristics are examined by using three different Reynolds numbers based on the nozzle exit height. Flow pattern is investigated on lateral and spanwise directions. Following the twin jet experiments, results are compared with those of offset jet flow. Then, the effect of a convex surface between two jet exits on the flow development is examined.Twin jet impingement on a flat surface is investigated. To examine the effect of the non-dimensional nozzle to plate distance (Y /H+) on the flow , experiments are performed for three different nozzle to plate distances (Y/H+=2, 4, 8). Resultant velocity and turbulence intensity profiles and pressure distributions on the plate are measured.The mean velocity and turbulence intensities are measured by using constanttemperature hot-wire anemometry. Flow visualization techniques as smokevisualization and surface oil film technique are used for qualitative investigation of flow pattern. Pressure distributions on the impingement plate are measured by means of the pressure tabs on the surface and a micro manometer.This study consists of five chapters. Chapter 1 is the introduction which outlines the objectives and the means of the study. Chapter 2 describes basic principles of the turbulent, incompressible jet flow structure and gives literature review of the experimental studies and recent advances on the characteristics of the flow. Experimental flow facility , instrumentation and experimental procedures are described in Chapter 3. Experimental results are presented in Chapter 4. Finally, conclusions are given in Chapter 5. .
Author: Zhujun Tang
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1460
Get Book Here
Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: P. S. Srinivasan
Publisher:
ISBN:
Category :
Languages : en
Pages : 564
Get Book Here
Book Description
