Modification of turbulence caused by cationic surfactant wormlike micellar structures in two-dimensional turbulent flow

2021 ◽  
Vol 933 ◽  
Author(s):  
Kengo Fukushima ◽  
Haruki Kishi ◽  
Hiroshi Suzuki ◽  
Ruri Hidema
Keyword(s):  
Turbulent Flow ◽  
Surfactant Solution ◽  
Turbulent Energy ◽  
Molar Ratio ◽  
Wormlike Micelles ◽  
Two Dimensional ◽  
Turbulence Statistics ◽  
Image Velocimetry ◽  
Set Up ◽  
Induced Structure

An experimental study is performed to investigate the effects of the extensional rheological properties of drag-reducing wormlike micellar solutions on the vortex deformation and turbulence statistics in two-dimensional (2-D) turbulent flow. A self-standing 2-D turbulent flow was used as the experimental set-up, and the flow was observed through interference pattern monitoring and particle image velocimetry. Vortex shedding and turbulence statistics in the flow were affected by the formation of wormlike micelles and were enhanced by increasing the molar ratio of the counter-ion supplier to the surfactant, ξ, or by applying extensional stresses to the solution. In the 2-D turbulent flow, extensional and shear rates were applied to the fluids around a comb of equally spaced cylinders. This induced the formation of a structure made of wormlike micelles just behind the cylinder. The flow-induced structure influenced the velocity fields around the comb and the turbulence statistics. A characteristic increase in turbulent energy was observed, which decreased slowly downstream. The results implied that the characteristic modification of the 2-D turbulent flow of the drag-reducing surfactant solution was affected by the formation and slow relaxation of the flow-induced structure. The relaxation process of the flow-induced structure made of wormlike micelles was very different from that of the polymers.

Relationship Between Velocity Field and Curvature of a Vortex in Two-Dimensional Turbulent Flow

2015 ◽  
Author(s):  
Ikumi Murao ◽  
Ruri Hidema ◽  
Hiroshi Suzuki ◽  
Yoshiyuki Komoda
Keyword(s):  
Velocity Field ◽  
Turbulent Flow ◽  
Particle Image ◽  
Soap Film ◽  
Flow Imaging ◽  
Two Dimensional ◽  
Test Bed ◽  
Flexible Polymer ◽  
Image Velocimetry ◽  
Film Interface

A flowing soap film is a promising test bed to generate two-dimensional turbulence dominated by an extensional stress field. In this study, the effects of visco-elastic fluid on two-dimensional (2D) turbulent flow have been quantified by the curvature of vortices visualized by a Film Interface Flow Imaging (FIFI) method in the flow. The curvatures of the vortices are related to the direction of velocity vector on the vortices. In order to confirm this idea, the velocity field of 2D turbulent flow was obtained by Particle Image Velocimetry (PIV). As a flexible polymer, polyethyleneoxide (PEO) was also added to the flow in order to observe how polymers vary the curvature histogram and velocity fields. From the results, it was found that the variance of the curvature histogram became lower by adding the polymer. This was also confirmed by the phenomena that the fluctuation of the velocity vectors in the normal direction becomes small by adding the polymer.

Vortex deformation and turbulent energy of polymer solution in a two-dimensional turbulent flow

2020 ◽  
Vol 285 ◽  
pp. 104385
Author(s):  
Ruri Hidema ◽  
Kengo Fukushima ◽  
Ryohei Yoshida ◽  
Hiroshi Suzuki
Keyword(s):  
Turbulent Flow ◽  
Polymer Solution ◽  
Turbulent Energy ◽  
Two Dimensional

Experimental investigation of unsteady separation in the rotor-oscillator flow

2018 ◽  
Vol 844 ◽  
pp. 546-566 ◽  
Author(s):  
Marc-Étienne Lamarche-Gagnon ◽  
Jérôme Vétel
Keyword(s):  
Particle Image ◽  
Rotating Cylinder ◽  
High Viscosity ◽  
Vortical Flow ◽  
Two Dimensional ◽  
Unsteady Separation ◽  
Image Velocimetry ◽  
Set Up ◽  
Viscosity Fluid ◽  
Unstable Direction

Visualisations of various types of flow separation are presented in an experimental set-up that translates a rotating cylinder parallel to a wall. Particle image velocimetry is used to measure the two velocity components in a plane perpendicular to the cylinder where the flow is two-dimensional. To spatially resolve the flow close to the wall, a high-viscosity fluid is used. For a periodic translation, the fixed separation is compared to the theory of Haller (J. Fluid Mech., vol. 512, 2004, pp. 257–311), while for non-periodic translations, a method is proposed to extract the moving separation point captured by a Lagrangian saddle point, and its finite-time unstable direction (separation profiles). Intermediate cases are also presented where both types of separation, fixed and moving, are either present simultaneously or appear successively. Some results issued from numerical simulations of an impinging jet show that all the cases observed in the rotor-oscillator flow are not restricted to high-viscosity fluid motions but may also occur within any vortical flow.

Analysis of Frost Growth through a Two-Dimensional Duct with Turbulent Flow

2008 ◽  
Vol 39 (4) ◽  
pp. 347-370
Author(s):  
M. Salmanpour ◽  
O. Nourani Zonouz ◽  
Mahmood Yaghoubi
Keyword(s):  
Turbulent Flow ◽  
Two Dimensional ◽  
Frost Growth

scholarly journals Energy budget in internal wave attractor experiments

2019 ◽  
Vol 880 ◽  
pp. 743-763 ◽  
Author(s):  
Géraldine Davis ◽  
Thierry Dauxois ◽  
Timothée Jamin ◽  
Sylvain Joubaud
Keyword(s):  
Velocity Field ◽  
Internal Wave ◽  
Boundary Layers ◽  
Energy Budget ◽  
Dissipation Rate ◽  
Theoretical Expression ◽  
Two Dimensional ◽  
Energy Sink ◽  
Set Up ◽  
Different Sources

The current paper presents an experimental study of the energy budget of a two-dimensional internal wave attractor in a trapezoidal domain filled with uniformly stratified fluid. The injected energy flux and the dissipation rate are simultaneously measured from a two-dimensional, two-component, experimental velocity field. The pressure perturbation field needed to quantify the injected energy is determined from the linear inviscid theory. The dissipation rate in the bulk of the domain is directly computed from the measurements, while the energy sink occurring in the boundary layers is estimated using the theoretical expression for the velocity field in the boundary layers, derived recently by Beckebanze et al. (J. Fluid Mech., vol. 841, 2018, pp. 614–635). In the linear regime, we show that the energy budget is closed, in the steady state and also in the transient regime, by taking into account the bulk dissipation and, more importantly, the dissipation in the boundary layers, without any adjustable parameters. The dependence of the different sources on the thickness of the experimental set-up is also discussed. In the nonlinear regime, the analysis is extended by estimating the dissipation due to the secondary waves generated by triadic resonant instabilities, showing the importance of the energy transfer from large scales to small scales. The method tested here on internal wave attractors can be generalized straightforwardly to any quasi-two-dimensional stratified flow.

Nanoparticle Precipitation in a T-Mixer: Coupling Experimental and Numerical Investigations of the Fluid Dynamics With the Solid Formation Processes

2006 ◽  
Author(s):  
Johannes Gradl ◽  
Florian Schwertfirm ◽  
Hans-Christoph Schwarzer ◽  
Hans-Joachim Schmid ◽  
Michael Manhart ◽  
...  
Keyword(s):  
Flow Field ◽  
Fluid Dynamic ◽  
Concentration Field ◽  
Population Balance ◽  
Mixing Process ◽  
Image Velocimetry ◽  
Modeling Material ◽  
Field Information ◽  
Set Up ◽  
3D Information

Mixing and consequently fluid dynamic is a key parameter to tailor the particle size distribution (PSD) in nanoparticle precipitation. Due to fast and intensive mixing a static T-mixer configuration is capable for synthesizing continuously nanoparticles. The flow and concentration field of the applied mixer is investigated experimentally at different flow rates by Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF). Due to the PIV measurements the flow field in the mixer was characterized qualitatively and the mixing process itself is quantified by the subsequent LIF-measurements. A special feature of the LIF set up is to detect structures in the flow field, which are smaller than the Batchelor length. Thereby a detailed insight into the mixing process in a static T-Mixer is given. In this study a CFD-based approach using Direct Numerical Simulation (DNS) in combination with the solid formation kinetics solving population balance equations (PBE) is applied, using barium sulfate as modeling material. A Lagrangian Particle Tracking strategy is used to couple the flow field information with a micro mixing model and with the classical theory of nucleation. We found that the DNS-PBE approach including macro and micro mixing, combined with the population balance is capable of predicting the full PSD in nanoparticle precipitation for different operating parameters. Additionally to the resulting PSD, this approach delivers a 3D-information about all running subprocesses in the mixer, i.e. supersaturation built-up or nucleation, which is visualized for different process variables.

Level set-based topology optimization for two dimensional turbulent flow using an immersed boundary method

2021 ◽  
pp. 110630
Author(s):  
Seiji Kubo ◽  
Atsushi Koguchi ◽  
Kentaro Yaji ◽  
Takayuki Yamada ◽  
Kazuhiro Izui ◽  
...  
Keyword(s):  
Topology Optimization ◽  
Turbulent Flow ◽  
Level Set ◽  
Immersed Boundary Method ◽  
Immersed Boundary ◽  
Two Dimensional ◽  
Boundary Method

scholarly journals E–ε Model of Spray-Laden Near-Sea Atmospheric Layer in High Wind Conditions

2014 ◽  
Vol 44 (2) ◽  
pp. 742-763 ◽  
Author(s):  
Yevgenii Rastigejev ◽  
Sergey A. Suslov
Keyword(s):  
Turbulent Flow ◽  
Drag Coefficient ◽  
Turbulent Mixing ◽  
Numerical Solutions ◽  
Turbulent Energy ◽  
Wave Crest ◽  
Mixing Length ◽  
High Wind ◽  
Close Proximity ◽  
Ocean Spray

Abstract In-depth understanding and accurate modeling of the interaction between ocean spray and a turbulent flow under high wind conditions is essential for improving the intensity forecasts of hurricanes and severe storms. Here, the authors consider the E–ε closure for a turbulent flow model that accounts for the effects of the variation of turbulent energy and turbulent mixing length caused by spray stratification. The obtained analytical and numerical solutions show significant differences between the current E–ε model and the lower-order turbulent kinetic energy (TKE) model considered previously. It is shown that the reduction of turbulent energy and mixing length above the wave crest level, where the spray droplets are generated, that is not accounted for by the TKE model results in a significant suppression of turbulent mixing in this near-wave layer. In turn, suppression of turbulence causes an acceleration of flow and a reduction of the drag coefficient that is qualitatively consistent with field observations if spray is fine (even if its concentration is low) or if droplets are large but their concentration is sufficiently high. In the latter case, spray inertia may become important. This effect is subsequently examined. It is shown that spray inertia leads to the reduction of wind velocity in the close proximity of the wave surface relative to the reference logarithmic profile. However, at higher altitudes the suppression of flow turbulence by the spray still results in the wind acceleration and the reduction of the local drag coefficient.

Experimental and Numerical Investigations of a Turbulent Flow Behavior in Isolated and Nonisolated Conical Diffusers

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
F. Aloui ◽  
E. Berrich ◽  
D. Pierrat
Keyword(s):  
Turbulent Flow ◽  
Flow Behavior ◽  
Piv Measurements ◽  
Numerical Investigations ◽  
Image Velocimetry ◽  
Sst Model ◽  
Proper Orthogonal ◽  
Hydraulic Circuits

In some industrial processes, and especially in agrofood industries, the cleaning in place mechanism used for hydraulic circuits plays an important role. This process needs a good knowledge of the hydrodynamic flows to determinate the appropriate parameters that assure a good cleaning of these circuits without disassembling them. Generally, different arrangements are present in these hydraulic circuits, such as expansions, diffusers, and elbows. The flow crossing these singularities strongly affects the process of cleaning in place. This work is then a contribution to complete recent studies of “aliments quality security” project to ameliorate the quality of the cleaning in place. It presents experimental and numerical investigations of a confined turbulent flow behavior across a conical diffuser (2α=16 deg). The role of a perturbation caused by the presence of an elbow in the test section, upstream of the progressive enlargement, was studied. The main measurements were the static pressure and the instantaneous velocity fields using the particle image velocimetry (PIV). Post-processing of these PIV measurements were adopted using the Γ2 criterion for the vortices detection and the proper orthogonal decomposition (POD) technique to extract the most energetic modes contained in the turbulent flow and to the turbulent flow filtering. A database has been also constituted and was used to test the validity of the most models of turbulence, and in particular, a variant of the shear stress transport (SST) model.

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