Investigation of Turbulent Mixing in a Macro-Scale Multi-Inlet Vortex Nanoprecipitation Reactor by Stereoscopic-PIV

2014 ◽  
Author(s):  
Zhenping Liu ◽  
James C. Hill ◽  
Rodney O. Fox ◽  
Michael G. Olsen
Keyword(s):  
Reynolds Number ◽  
Turbulent Mixing ◽  
Three Dimensional ◽  
Stereoscopic Particle Image Velocimetry ◽  
Vortex Center ◽  
Mean Velocity ◽  
Vortex Model ◽  
Functional Nanoparticles ◽  
Turbulent Characteristics ◽  
Macro Scale

Flash Nanoprecipitation (FNP) is a technique to produce monodisperse functional nanoparticles through rapidly mixing a saturated solution and a non-solvent. Multi-inlet vortex reactors (MIVR) have been effectively applied to FNP due to their ability to provide both rapid mixing and the flexibility of inlet flow conditions. Until recently, only micro-scale MIVRs have been demonstrated to be effective in FNP. A scaled-up MIVR could potentially generate large quantities of functional nanoparticles, giving FNP wider applicability in the industry. In the present research, turbulent mixing inside a scaled-up, macro-scale MIVR was measured by stereoscopic particle image velocimetry (SPIV). Reynolds number of this reactor is defined based on the bulk inlet velocity, ranging from 3290 to 8225. It is the first time that the three-dimensional velocity field of a MIVR was experimentally measured. The influence of Reynolds number on mean velocity becomes more linear as Reynolds number increases. An analytical vortex model was proposed to well describe the mean velocity profile. The turbulent characteristics such as turbulent kinematic energy and Reynolds stress are also presented. The wandering motion of vortex center was found to have a significant contribution to the turbulent kinetic energy of flow near the center area.

A Batchelor Vortex Model for Mean Velocity of Turbulent Swirling Flow in a Macroscale Multi-Inlet Vortex Reactor

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Zhenping Liu ◽  
Rodney O. Fox ◽  
James C. Hill ◽  
Michael G. Olsen
Keyword(s):  
Reynolds Number ◽  
Simple Model ◽  
Velocity Field ◽  
Swirling Flow ◽  
Stereoscopic Particle Image Velocimetry ◽  
Mean Velocity ◽  
Vortex Model ◽  
Nonlinear Curve Fitting ◽  
Image Velocimetry ◽  
Vortex Reactor

The velocity field in a macroscale multi-inlet vortex reactor (MIVR) used in “flash nanoprecipitation (FNP)” process for producing functional nanoparticles was investigated using stereoscopic particle image velocimetry (SPIV). Based on the experimental data, a simple model was proposed to describe the average velocity field within the reactor. In the model, the axial and azimuthal velocities could be well described by the combination of two coflowing Batchelor vortices. In this model, six dimensionless coefficients are identified by nonlinear curve fitting, and their dependence on Reynolds number can be linearly described. This simple model is able to accurately predict the mean velocity field within the confined turbulent swirling flow based purely on Reynolds number.

Computation of Flow and Heat Transfer in Rotating Rectangular Channels (AR=4:1) With Pin-Fins by a Reynolds Stress Turbulence Model

2006 ◽  
Vol 129 (6) ◽  
pp. 685-696 ◽  
Author(s):  
Guoguang Su ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Density Ratio ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Pin Fins

Computations with multi-block chimera grids were performed to study the three-dimensional turbulent flow and heat transfer in a rotating rectangular channel with staggered arrays of pin-fins. The channel aspect ratio (AR) is 4:1, the pin length to diameter ratio (H∕D) is 2.0, and the pin spacing to diameter ratio is 2.0 in both the stream-wise (S1∕D) and span-wise (S2∕D) directions. A total of six calculations have been performed with various combinations of rotation number, Reynolds number, and coolant-to-wall density ratio. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.122 to 0.20, respectively, while the Reynolds number varied from 10,000 to 100,000. For the rotating cases, the rectangular channel was oriented at 150deg with respect to the plane of rotation to be consistent with the configuration of the gas turbine blade. A Reynolds-averaged Navier-Stokes (RANS) method was employed in conjunction with a near-wall second-moment turbulence closure for detailed predictions of mean velocity, mean temperature, and heat transfer coefficient distributions.

A resonance mechanism in plane Couette flow

1980 ◽  
Vol 98 (1) ◽  
pp. 149-159 ◽  
Author(s):  
L. HÅKan Gustavsson ◽  
Lennart S. Hultgren
Keyword(s):  
Reynolds Number ◽  
Couette Flow ◽  
Velocity Component ◽  
Three Dimensional ◽  
Phase Speed ◽  
Maximum Amplitude ◽  
Streamwise Velocity ◽  
Plane Couette Flow ◽  
Mean Velocity ◽  
Streamwise Velocity Component

The temporal evolution of small three-dimensional disturbances on viscous flows between parallel walls is studied. The initial-value problem is formally solved by using Fourier–Laplace transform techniques. The streamwise velocity component is obtained as the solution of a forced problem. As a consequence of the three-dimensionality, a resonant response is possible, leading to algebraic growth for small times. It occurs when the eigenvalues of the Orr–Sommerfeld equation coincide with the eigenvalues of the homogeneous operator for the streamwise velocity component. The resonance has been investigated numerically for plane Couette flow. The phase speed of the resonant waves equals the average mean velocity. The wavenumber combination that leads to the largest amplitude corresponds to structures highly elongated in the streamwise direction. The maximum amplitude, and the time to reach this maximum, scale with the Reynolds number. The aspect ratio of the most rapidly growing wave increases with the Reynolds number, with its spanwise wavelength approaching a constant value of about 3 channel heights.

Computation of Flow and Heat Transfer in Rotating Rectangular Channels (AR=4:1) With Pin-Fins by a Reynolds Stress Turbulence Model

2005 ◽  
Author(s):  
Guoguang Su ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Density Ratio ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Pin Fins

Computations with multi-block chimera grids were performed to study the three-dimensional turbulent flow and heat transfer in a rotating rectangular channel with staggered arrays of pin-fins. The channel aspect ratio (AR) is 4:1, the pin length to diameter ratio (H/D) is 2.0, and the pin spacing to diameter ratio is 2.0 in both the stream-wise (S1/D) and span-wise (S2/D) directions. A total of six calculations have been performed with various combinations of rotation number, Reynolds number, and coolant-to-wall density ratio. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.122 to 0.20, respectively, while the Reynolds number varied from 10,000 to 100,000. For the rotating cases, the rectangular channel was oriented at 150 deg with respect to the plane of rotation to be consistent with the configuration of the gas turbine blade. A Reynolds-Averaged Navier-Stokes (RANS) method was employed in conjunction with a near-wall second-moment turbulence closure for detailed predictions of mean velocity, mean temperature, and heat transfer coefficient distributions.

scholarly journals Influence of initial turbulence level on the flow and sound fields of a subsonic jet at a diameter-based Reynolds number of 105

2012 ◽  
Vol 701 ◽  
pp. 352-385 ◽  
Author(s):  
C. Bogey ◽  
O. Marsden ◽  
C. Bailly
Keyword(s):  
Reynolds Number ◽  
Nozzle Exit ◽  
Structural Characteristics ◽  
Three Dimensional ◽  
Shear Layers ◽  
Linear Instability ◽  
Mean Velocity ◽  
Sound Fields ◽  
First Case ◽  
Initial Turbulence

AbstractFive isothermal round jets at Mach number $M= 0. 9$ and Reynolds number ${\mathit{Re}}_{D} = 1{0}^{5} $ originating from a pipe nozzle are computed by large-eddy simulations to investigate the effects of initial turbulence on flow development and noise generation. In the pipe, the boundary layers are untripped in the first case and tripped numerically in the four others in order to obtain, at the exit, mean velocity profiles similar to a Blasius laminar profile of momentum thickness equal to 1.8 % of the jet radius, yielding Reynolds number ${\mathit{Re}}_{\theta } = 900$, and peak turbulence levels ${ u}_{e}^{\ensuremath{\prime} } $ around 0, 3 %, 6 %, 9 % or 12 % of the jet velocity ${u}_{j} $. As the initial turbulence intensity increases, the shear layers develop more slowly with much lower root-mean-square (r.m.s.) fluctuating velocities, and the jet potential cores are longer. Velocity disturbances downstream of the nozzle exit also exhibit different structural characteristics. For low ${ u}_{e}^{\ensuremath{\prime} } / {u}_{j} $, they are dominated by the first azimuthal modes ${n}_{\theta } = 0$, 1 and 2, and show significant skewness and intermittency. The growth of linear instability waves and a first stage of vortex pairings occur in the shear layers for ${ u}_{e}^{\ensuremath{\prime} } / {u}_{j} \leq 6\hspace{0.167em} \% $. For higher ${ u}_{e}^{\ensuremath{\prime} } / {u}_{j} $, three-dimensional features and high azimuthal modes prevail, in particular close to the nozzle exit where the wavenumbers naturally found in turbulent wall-bounded flows clearly appear. Concerning the sound fields, strong broadband components mainly associated with mode ${n}_{\theta } = 1$ are noticed around the pairing frequency for the untripped jet. With rising ${ u}_{e}^{\ensuremath{\prime} } / {u}_{j} $, however, they become weaker, and the noise levels decrease asymptotically down to those measured for jets at ${\mathit{Re}}_{D} \geq 5\ensuremath{\times} 1{0}^{5} $, which are likely to be initially turbulent and to emit negligible vortex-pairing noise. These results correspond well to experimental observations, made separately for either mixing layers, jet flow or sound fields.

Investigation of effects of compressibility, geometric and flow parameters on the simulation of a synthetic jet behaviour

2016 ◽  
Vol 120 (1225) ◽  
pp. 521-546 ◽  
Author(s):  
F. Bazdidi-Tehrani ◽  
A. Abouata ◽  
M. Hatami ◽  
N. Bohlooli
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Mass Flow ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Synthetic Jet ◽  
Instantaneous Velocity ◽  
Mean Velocity ◽  
Velocity Magnitude ◽  
Flow Parameters

ABSTRACTThe present paper focuses on a three-dimensional unsteady turbulent synthetic jet to assess the accuracy of a compressible simulation and some important parameters including the simulations of the actuator, cavity height and Reynolds number. The two-equationSST/k− ω turbulence model is used to predict the flow behaviour. Results show that the compressible simulation case is more accurate than the incompressible one and the dynamic mesh exhibits more reliable results than the mass flow inlet boundary in the compressible simulation. The compressible case displays a delay in the phase of instantaneous velocity for all three Reynolds numbers. Also, the maximum of mean velocity is less than the incompressible case. Moreover, an increase in the Reynolds number leads to an amplification of the peak of mean velocity magnitude. Finally, results demonstrate that a reduction in the cavity height regarding the compressible simulation case causes a reduction in the phase delay and rise in peak of instantaneous velocity magnitude.

Experimental Study of Reynolds Number Effects on Three-Dimensional Offset Jets

2014 ◽  
Author(s):  
Zacharie M. J. Durand ◽  
Shawn P. Clark ◽  
Mark F. Tachie ◽  
Jarrod Malenchak ◽  
Getnet Muluye
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Shear Stresses ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Reynolds Number Effects

The effect of Reynolds number on three-dimensional offset jets was investigated in this study. An acoustic Doppler velocimeter simultaneously measured all three components of velocity, U, V and W, and turbulence intensity, urms, vrms, and wrms, and all three Reynolds shear stresses, uv, uw, and vw. Turbulent kinetic energy, k, was calculated with all three values of turbulence intensities. Flow measurements were performed at Reynolds numbers of 34,000, 53,000 and 86,000. Results of this experimental study indicate the wall-normal location of maximum mean velocity and jet spread to be independent of Reynolds number. The effects on maximum mean velocity decay are reduced with increasing Reynolds number. Profiles of mean velocities, U, V and W, turbulence intensities, urms, vrms, and wrms, and turbulent kinetic energy, k, show independence of Reynolds number. Reynolds shear stress uv was independent of Reynolds number while the magnitude of uw was reduced at higher Reynolds number.

Global frequency selection in the observed time-mean wakes of circular cylinders

2008 ◽  
Vol 601 ◽  
pp. 425-441 ◽  
Author(s):  
MOSES KHOR ◽  
JOHN SHERIDAN ◽  
MARK C. THOMPSON ◽  
KERRY HOURIGAN
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Linear Instability ◽  
Circular Cylinders ◽  
Near Wake ◽  
Mean Velocity ◽  
Number Range ◽  
Wake Instability ◽  
Karman Vortex

Observations have been made of the time-mean velocity profile at midspan in the near-wake of circular cylinders at moderate Reynolds numbers between 600 and 4600, well beyond the Reynolds number of approximately 200 at which the wake becomes three-dimensional. The measured profiles are found to be represented quite accurately by a family of function profiles with known linear instability characteristics. The complex instability frequency is then determined as a function of wake position, using the function profiles. In general, the near wake undergoes a transition from convective to absolute instability; the distance downstream to the point of transition is found to increase over the Reynolds number range investigated. The emergence of a significant region of convective instability is consistent with the known appearance of Bloor–Gerrard vortices. The selected frequency of the wake instability is determined by the saddle-point criterion; the Strouhal numbers for Bénard–von Kármán vortex shedding are found to compare well with the values in the literature.

Effects of Guide-Vane Number in a Three-Dimensional 60-Deg Curved Side-Dump Combustor Inlet

2000 ◽  
Vol 123 (2) ◽  
pp. 211-218 ◽  
Author(s):  
Tong-Miin Liou ◽  
Hsin-Li Lee ◽  
Chin-Chun Liao
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Laser Doppler Velocimetry ◽  
Guide Vane ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Mean Velocity ◽  
Guide Vanes ◽  
Aspect Ratios ◽  
The One

Three-dimensional flowfields in a 60-deg curved combustor inlet duct of rectangular cross-section with and without guide vanes were measured using Laser-Doppler velocimetry for the longitudinal, radial, and spanwise velocity components. The Reynolds number based on the bulk mean velocity and hydraulic diameter was 2.53×104. The main parameters examined were the guide-vane number and Reynolds number. The results show that to completely eliminate flow separation in the curved combustor inlet three guide vanes should be installed. The critical Reynolds number for the absence of the flow separation is found to decrease with increasing product of radius and aspect ratios. In addition, it is found that in most regions the maximum radial mean velocity, difference between radial and spanwise normal stress, and the turbulent kinetic energy decrease with increasing guide-vane number. A rationale for the absence of flow separation in the one-vane case predicted by previous researchers is also provided.

Effects of Reynolds Number on Turbulent Characteristics of Surface Jet

2016 ◽  
Author(s):  
M. S. Rahman ◽  
M. F. Tachie
Keyword(s):  
Reynolds Number ◽  
Reynolds Shear Stress ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Mean Velocity ◽  
Potential Core ◽  
Turbulent Characteristics ◽  
Reynolds Number Effects ◽  
Surface Jet ◽  
Jet Characteristics

Experimental study was carried out to investigate the Reynolds number effects on surface jet characteristics. The surface jet was produced using orifice nozzle with offset height ratio of 2. Six different Reynolds numbers ranging from 2300 to 11900 were investigated. Potential core region of the jet decreased with Reynolds number up to the Reynolds number of 5500. Reattachment point was sensitive to Reynolds number within the range of the present study. The maximum velocity decay and jet spread were nearly independent of Reynolds number. The streamwise mean velocity, streamwise turbulence intensity and Reynolds shear stress distribution along surface-normal direction were affected by the free surface and showed Reynolds number independency at the Reynolds numbers beyond 5500.

Sign in / Sign up

Export Citation Format

Share Document