scholarly journals Study on the characteristics of the pressure fluctuations and their contribution to turbulence kinetic energy

2021 ◽  
pp. 105634
Author(s):  
Zhuorui Wei ◽  
Hongsheng Zhang ◽  
Yan Ren ◽  
Qianhui Li ◽  
Xuhui Cai ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Pressure Fluctuations ◽  
Turbulence Kinetic Energy

Composited structure of shallow cumulus clouds

2021 ◽  
Author(s):  
Chris Holloway ◽  
Jian-Feng Gu ◽  
Bob Plant ◽  
Todd Jones
Keyword(s):  
Kinetic Energy ◽  
Vertical Velocity ◽  
Inversion Layer ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Theoretical Models ◽  
Turbulence Kinetic Energy ◽  
Cloud Base ◽  
Asymmetric Structures ◽  
Negatively Buoyant

<div> <div> <div> <div> <p>The normalized distributions of thermodynamic and dynamical variables both within and outside shallow clouds are investigated through a composite algorithm using large eddy simulation of the BOMEX case. The normalized magnitude is maximum near cloud center and decreases outwards. While relative humidity (RH) and cloud liquid water (<em>q<sub>l </sub></em>) decrease smoothly to match the environment, the vertical velocity, virtual potential temperature (<em>θ<sub>v </sub></em>) and potential temperature (<em>θ</em>) perturbations have more complicated behaviour towards the cloud boundary. Below the inversion layer, <em>θ<sub>v</sub></em> becomes <span>negative before the vertical velocity has turned from updraft to subsiding shell outside the cloud, indicating the presence of a transition zone where the updraft is negatively buoyant. Due to the downdraft outside the cloud and the enhanced horizontal turbulent mixing across the edge, the normalized turbulence kinetic energy (TKE) and horizontal turbulence kinetic energy (HTKE) decrease more slowly from the cloud center outwards than the thermodynamic variables. The distributions all present asymmetric structures in response to the vertical wind shear, with more negatively buoyant air, stronger downdrafts and larger TKE on the downshear side. We discuss several implications of the distributions for theoretical models and parameterizations. Positive buoyancy near cloud base is mostly due to </span><span>the virtual effect of water vapor, emphasising the role of moisture in triggering. The mean vertical velocity is found </span><span>to be approximately half the maximum vertical velocity within each cloud, providing a constraint on some models. Finally, products of normalized distributions for different variables are shown to be able to well represent the vertical heat and moisture fluxes, but they underestimate fluxes in the inversion layer because they do not capture cloud top downdrafts.</span></p> </div> </div> </div> </div>

Numerical Simulation of Transient Flow Inside Nozzle on Gasoline Direct Injection Engine

2012 ◽  
Vol 466-467 ◽  
pp. 1237-1241
Author(s):  
Yan Hua Wang ◽  
Shi Chun Yang ◽  
Yun Qing Li
Keyword(s):  
Kinetic Energy ◽  
Transient Flow ◽  
Direct Injection ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Turbulence Kinetic Energy ◽  
Gasoline Direct Injection ◽  
Injection Hole ◽  
Gasoline Direct Injection Engine ◽  
Nozzle Configuration

To achieve transient flow characteristics at exit of nozzle orifice on gasoline direct injection engine, two phase Euler-Euler schemes was used to simulate the internal flow of the swirl nozzle. Different flow characteristics were calculated in the simulation. Different kinds of nozzle configuration were studied. Cavitaion and swirl flow occured in the nozzles. Injection hole configuration matters more than area variation of swirl tangential slot to discharge coefficient of the studied nozzle. Discharge coefficient changes a little along the injection hole length. The area of the swirl tangrntial slot plays an important throttling action in nozzle internal flow. Smaller area of swirl tangential slot generates larger degree cavitation but smaller mean injection velocity. Turbulence kinetic energy changes with the time of cavitation and swirl field occurring and the nozzle configuration. Before the appearance of cavitation, smaller inclination angle of orifice can generate more turbulence kinetic energy. After that moment, turbulence kinetic energy varies with different configuration. Along injection hole length, turbulence kinetic energy obviously varies. These flow characteristics affect primary atomization and will be as input for next spray simulation. They are also applied to design reference for injection nozzle.

scholarly journals A Comparative Assessment of Spalart-Shur Rotation/Curvature Correction in RANS Simulations in a Centrifugal Pump Impeller

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Ran Tao ◽  
Ruofu Xiao ◽  
Wei Yang ◽  
Fujun Wang
Keyword(s):  
Kinetic Energy ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Comparative Assessment ◽  
Turbulence Kinetic Energy ◽  
Low Flow ◽  
Pump Impeller ◽  
Curvature Correction ◽  
Centrifugal Pump Impeller ◽  
Low Flow Rate

RANS simulation is widely used in the flow prediction of centrifugal pumps. Influenced by impeller rotation and streamline curvature, the eddy viscosity models with turbulence isotropy assumption are not accurate enough. In this study, Spalart-Shur rotation/curvature correction was applied on the SSTk-ωturbulence model. The comparative assessment of the correction was proceeded in the simulations of a centrifugal pump impeller. CFD results were compared with existing PIV and LDV data under the design and low flow rate off-design conditions. Results show the improvements of the simulation especially in the situation that turbulence strongly produced due to undesirable flow structures. Under the design condition, more reasonable turbulence kinetic energy contour was captured after correction. Under the low flow rate off-design condition, the prediction of turbulence kinetic energy and velocity distributions became much more accurate when using the corrected model. So, the rotation/curvature correction was proved effective in this study. And, it is also proved acceptable and recommended to use in the engineering simulations of centrifugal pump impellers.

scholarly journals Variation of diurnal Turbulence Kinetic Energy using sonic anemometer observation: a case study Ledeng, Bandung

2018 ◽  
Author(s):  
Sandy Hardian Susanto Herho ◽  
Dasapta Erwin Irawan
Keyword(s):  
Kinetic Energy ◽  
Diurnal Variation ◽  
Wind Velocity ◽  
Sonic Anemometer ◽  
Diurnal Variations ◽  
Turbulence Kinetic Energy ◽  
Atmospheric Conditions

Sonic anemometer observation was performed on 29 - 30 September 2014 in Ledeng, Bandung to see diurnal variations of Turbulence Kinetic Energy (TKE) that occurred in this area. The measured sonic anemometer was the wind velocity components u, v, and w. From the observation result, it can be seen that the diurnal variation that happened was quite significant. The maximum TKE occurs during the daytime when atmospheric conditions tend to be unstable. TKE values were small at night when atmospheric conditions are more stable than during the daytime.

scholarly journals Turbulence Adjustment and Scaling in an Offshore Convective Internal Boundary Layer: A CASPER Case Study

2020 ◽  
Vol 77 (5) ◽  
pp. 1661-1681
Author(s):  
Qingfang Jiang ◽  
Qing Wang ◽  
Shouping Wang ◽  
Saša Gaberšek
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Kinetic Energy ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Internal Boundary Layer ◽  
Turbulence Kinetic Energy ◽  
Internal Boundary ◽  
Field Observations ◽  
The Mean

Abstract The characteristics of a convective internal boundary layer (CIBL) documented offshore during the East Coast phase of the Coupled Air–Sea Processes and Electromagnetic Ducting Research (CASPER-EAST) field campaign has been examined using field observations, a coupled mesoscale model (i.e., Navy’s COAMPS) simulation, and a couple of surface-layer-resolving large-eddy simulations (LESs). The Lagrangian modeling approach has been adopted with the LES domain being advected from a cool and rough land surface to a warmer and smoother sea surface by the mean offshore winds in the CIBL. The surface fluxes from the LES control run are in reasonable agreement with field observations, and the general CIBL characteristics are consistent with previous studies. According to the LESs, in the nearshore adjustment zone (i.e., fetch < 8 km), the low-level winds and surface friction velocity increase rapidly, and the mean wind profile and vertical velocity skewness in the surface layer deviate substantially from the Monin–Obukhov similarity theory (MOST) scaling. Farther offshore, the nondimensional vertical wind shear and scalar gradients and higher-order moments are consistent with the MOST scaling. An elevated turbulent layer is present immediately below the CIBL top, associated with the vertical wind shear across the CIBL top inversion. Episodic shear instability events occur with a time scale between 10 and 30 min, leading to the formation of elevated maxima in turbulence kinetic energy and momentum fluxes. During these events, the turbulence kinetic energy production exceeds the dissipation, suggesting that the CIBL remains in nonequilibrium.

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