scholarly journals Scaling of Droplet Breakup in High-Pressure Homogenizer Orifices. Part II: Visualization of the Turbulent Droplet Breakup

2021 ◽  
Vol 5 (2) ◽  
pp. 31
Author(s):  
Benedikt Mutsch ◽  
Felix Johannes Preiss ◽  
Teresa Dagenbach ◽  
Heike Petra Karbstein ◽  
Christian J. Kähler
Keyword(s):  
Turbulent Flow ◽  
Density Ratio ◽  
Droplet Breakup ◽  
Optical Measurements ◽  
Turbulent Flow Regime ◽  
Geometric Scaling ◽  
Macro Scale ◽  
Flow Motion ◽  
Original Scale ◽  
High Pressure Homogenizer

Emulsion formation is of great interest in the chemical and food industry and droplet breakup is the key process. Droplet breakup in a quiet or laminar flow is well understood, however, actual industrial processes are always in the turbulent flow regime, leading to more complex droplet breakup phenomena. Since high resolution optical measurements on microscopic scales are extremely difficult to perform, many aspects of the turbulent droplet breakup are physically unclear. To overcome this problem, scaled experimental setups (with scaling factors of 5 and 50) are used in conjunction with an original scale setup for reference. In addition to the geometric scaling, other non-dimensional numbers such as the Reynolds number, the viscosity ratio and the density ratio were kept constant. The scaling allows observation of the phenomena on macroscopic scales, whereby the objective is to show that the scaling approach makes it possible to directly transfer the findings from the macro- to the micro-/original scale. In this paper, which follows Part I where the flow fields were compared and found to be similar, it is shown by breakup visualizations that the turbulent droplet breakup process is similar on all scales. This makes it possible to transfer the results of detailed parameter variations investigated on the macro scale to the micro scale. The evaluation and analysis of the results imply that the droplet breakup is triggered and strongly influenced by the intensity and scales of the turbulent flow motion.

Thermal performance analysis of plate fin arrays with hexagonal perforations under turbulent flow regime

2019 ◽  
Author(s):  
Imtiaz Taimoor ◽  
Md Lutfor Rahman ◽  
Nazneen Sultana Aankhy ◽  
Muzahid Bin Khalid
Keyword(s):  
Performance Analysis ◽  
Turbulent Flow ◽  
Flow Regime ◽  
Thermal Performance ◽  
Turbulent Flow Regime

Influence of different flow regimes on the performance characteristics of a four-pad hydrostatic squeeze film damper loaded between pads

2019 ◽  
Vol 71 (3) ◽  
pp. 440-446
Author(s):  
Amina Nemchi ◽  
Ahmed Bouzidane ◽  
Aboubakeur Benariba ◽  
Hicham Aboshighiba
Keyword(s):  
Turbulent Flow ◽  
Load Capacity ◽  
Flow Regimes ◽  
Performance Characteristics ◽  
Squeeze Film ◽  
Eccentricity Ratio ◽  
Flow Conditions ◽  
Content Type ◽  
Turbulent Flow Regime ◽  
Squeeze Film Dampers

Purpose The purpose of this paper is to study the influence of different flow regimes on the dynamic characteristics of four-pad hydrostatic squeeze film dampers (SFDs) loaded between pads. Design/methodology/approach A numerical model based on Constantinescu’s turbulent lubrication theory using the finite difference method has been developed and presented to study the effect of eccentricity ratio on the performance characteristics of four-pad hydrostatic SFDs under different flow regimes. Findings It was found that the influence of turbulent flow on the dimensionless damping of four-pad hydrostatic SFDs appears to be essentially controlled by the eccentricity ratio. It was also found that the laminar flow presents higher values of load capacity compared to bearings operating under turbulent flow conditions. Originality/value In fact, the results obtained show that the journal bearing performances are significantly influenced by the turbulent flow regime. The study is expected to be useful to bearing designers.

Loss Characteristics of Orifices and Nozzles

1978 ◽  
Vol 100 (3) ◽  
pp. 299-307 ◽  
Author(s):  
S. H. Alvi ◽  
K. Sridharan ◽  
N. S. Lakshmana Rao
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Flow Regime ◽  
Discharge Coefficient ◽  
Critical Reynolds Number ◽  
Reynolds Numbers ◽  
Center Line ◽  
Laminar Regime ◽  
Variation Of Parameters ◽  
Turbulent Flow Regime

Loss characteristics of sharp-edged orifices, quadrant-edged orifices for varying edge radii, and nozzles are studied for Reynolds numbers less than 10,000 for β ratios from 0.2 to 0.8. The results may be reliably extrapolated to higher Reynolds numbers. Presentation of losses as a percentage of meter pressure differential shows that the flow can be identified into fully laminar regime, critical Reynolds number regime, relaminarization regime, and turbulent flow regime. An integrated picture of variation of parameters such as discharge coefficient, loss coefficient, settling length, pressure recovery length, and center line velocity confirms this classification.

Investigation of Flow Dynamics Over Transitional-Type Microcavity

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Paulius Vilkinis ◽  
Nerijus Pedišius ◽  
Mantas Valantinavičius
Keyword(s):  
Turbulent Flow ◽  
Flow Regime ◽  
Recirculation Zone ◽  
Transitional Flow ◽  
Navier Stokes ◽  
Flow Topology ◽  
Rans Equations ◽  
Recirculation Flow ◽  
Turbulent Flow Regime ◽  
Transitional Type

Flow over a transitional-type cavity in microchannels is studied using a microparticle image velocimetry system (μPIV) and commercially available computational fluid dynamics (CFD) software in laminar, transitional, and turbulent flow regimes. According to experimental results, in the transitional-type cavity (L/h1 = 10) and under laminar flow in the channel, the recirculation zone behind the backward-facing step stretches linearly with ReDh until the reattachment point reaches the middle of the cavity at xr/L = (0.5 to 0.6). With further increase in ReDh, the forward-facing step lifts the reattaching flow from the bottom of the cavity and stagnant recirculation flow fills the entire space of the cavity. Flow reattachment to the bottom of the cavity is again observed only after transition to the turbulent flow regime in the channel. Reynolds-averaged Navier–Stokes (RANS) equations and large eddy simulation (LES) results revealed changes in vortex topology, with the flow regime changing from laminar to turbulent. During the turbulent flow regime in the recirculation zone, periodically recurring vortex systems are formed. Experimental and computational results have a good qualitative agreement regarding the changes in the flow topology. However, the results of numerical simulations based on RANS equations and the Reynolds-stress-baseline turbulence model (RSM-BSL), show that computed reattachment length values overestimate the experimentally obtained values. The RSM-BSL model underestimates the turbulent kinetic energy intensity, generated by flow separation phenomena, on the stage of transitional flow regime.

scholarly journals Fast spectral solutions of the double-gyre problem in a turbulent flow regime

2019 ◽  
Vol 66 ◽  
pp. 745-767
Author(s):  
S. Elnaz Naghibi ◽  
Sergey A. Karabasov ◽  
Mir A. Jalali ◽  
S.M. Hadi Sadati
Keyword(s):  
Turbulent Flow ◽  
Flow Regime ◽  
Turbulent Flow Regime ◽  
Double Gyre

Micro-Scale Acoustic Streaming Pump Performance Characteristics

2000 ◽  
Author(s):  
Kenneth D. Frampton ◽  
Shawn E. Martin
Keyword(s):  
Acoustic Streaming ◽  
Excitation Amplitude ◽  
Frequency Variation ◽  
Micro Scale ◽  
Model Compression ◽  
Geometric Scaling ◽  
Macro Scale ◽  
Mass Flow Rates ◽  
Static Head ◽  
Mason’S Model

Abstract Acoustic streaming theory, applied to micro-scale pumps is presented. A mathematical model based on streaming equations and Mason’s model [9] of the piezoelectric transducer is described. Using this model, the effect of geometric scaling, frequency variation, and excitation amplitude on head and flow rate are examined. The significance of high body forces in the AC boundary layer are demonstrated, along with their effect on mass flow rates for small geometries. It is shown that flow velocities are inversely proportional to the flow tube diameter for small sizes. Experimental data for a macro-scale pump is provided and used to corroborate the static head versus excitation relationship predicted by the model. Compression wave acoustic streaming pumps are shown to have potential viability for micro-scale applications.

Sign in / Sign up

Export Citation Format

Share Document