scholarly journals Study on the 3D Hydrodynamic Characteristics and Velocity Uniformity of a Gravity Flow Circular Flume

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 927
Author(s):  
Yi Zhang ◽  
Longxi Han ◽  
Lina Chen ◽  
Chenfang Wang ◽  
Bo Chen ◽  
...  
Keyword(s):  
Flow Field ◽  
Environmental Science ◽  
Structural Characteristics ◽  
Longitudinal Velocity ◽  
Flow Characteristics ◽  
Science Research ◽  
Hydrodynamic Characteristics ◽  
Straight Channel ◽  
Uniformity Coefficient ◽  
Annular Flume

Flumes have been widely used in water conservancy science and environmental science research. It is of great significance to obtain the hydrodynamic characteristics and flow field uniformity in the flume. In this study, a new type of annular flume was taken as an example. The 3D flow field was simulated by using a commercial computational fluid dynamics (CFD) code, and was also measured by acoustic doppler velocimeter (ADV) to verify the simulation results. The average relative error range was between 8.37% and 9.95%, the simulated results basically reflected the actual situation of the flow field. On this basis, the structural characteristics of flow field were analyzed. A new calculation method of flow velocity uniformity was presented according to the flow characteristics of natural open channels. The velocity uniformity in the straight channel was calculated and analyzed based on this method, and the influence of speed on the velocity uniformity was further discussed. The length of uniform section was negatively correlated with the rotational speed (average velocity), which was between 39 cm and 101 cm in the straight, and the uniformity coefficient was less than 10%. Finally, the water flow characteristics in the straight channel without wheel were compared with the natural open channel flow. The longitudinal velocity was well fitted with the Prandtl logarithmic distribution formula (R2 > 0.977), and the application feasibility of the flume was analyzed. This study can provide technical support for the development and application of annular flume.

Artificially Thickened Turbulent Boundary Layers for Studying Heat Transfer and Skin Friction on Rough Surfaces

1983 ◽  
Vol 105 (2) ◽  
pp. 146-153 ◽  
Author(s):  
P. M. Ligrani ◽  
R. J. Moffat ◽  
W. M. Kays
Keyword(s):  
Skin Friction ◽  
Boundary Layers ◽  
Structural Characteristics ◽  
Turbulent Transport ◽  
Longitudinal Velocity ◽  
Hydrodynamic Characteristics ◽  
Rough Boundary ◽  
Turbulent Prandtl Number ◽  
Velocity Fluctuations ◽  
Normal Behavior

Thermal and hydrodynamic characteristics of boundary layers developing over uniform spheres roughness with momentum thicknesses as large as 1.43 cm are presented. To obtain thick hydrodynamic boundary layers, an artificial thickening device is employed. The normalized velocity and turbulence profiles produced using this device are two-dimensional and self-preserving. The turbulent transport and structural characteristics are representative of normal behavior to the level of spectra of the longitudinal velocity fluctuations. In the artificially thickened layers, the effect of the unheated starting length (ξ > 0, Δ < δ) on thermal boundary layer properties is present. Turbulent Prandtl number profiles are generally unaffected by the magnitude of the unheated starting length, whereas measured Stanton numbers, show different behavior as the unheated starting length varies. In thermal boundary layers which would have the same thickness as the augmented hydrodynamic layers (Δ ≃ δ), Stanton numbers are shown to be the same as skin friction coefficients, and are then provided for boundary layers much thicker than those previously studied. As fully rough boundary layers develop downstream and δ/ks increases, Cf/2 is proportional to δ2−b where b = 0.175. In order for such U∞ = constant, thick, rough wall layers to develop far enough downstream to reach smooth behavior where b = 0.250, ks Uτ/ν must become small, and b must increase from 0.175 to become greater than 0.250 in the transitionally rough regime.

scholarly journals Comparative Study on Flow Characteristics of Pipeline System Based on CFD

2021 ◽  
Vol 252 ◽  
pp. 02053
Author(s):  
Hou Yingzhe ◽  
Wu Hao ◽  
Yan Xiaozhe ◽  
Zhu Haoqiang ◽  
Gao Haitao ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Simulation Method ◽  
Hot Water ◽  
Pipeline System ◽  
Uniformity Coefficient ◽  
Study Results ◽  
Pipeline Vibration

Based on the CFD numerical simulation method, this paper established a pipeline model to study the internal flow characteristics of three different combinations of hot water pipeline systems and thus obtained the flow field information such as pressure, flow rate, and flow rate inside the pipeline. The study results showed that the smoother the pipeline transition, the smaller the velocity uniformity coefficient; the higher the uniformity of the flow field, the smaller the pressure and velocity fluctuations, the smaller the resulting pipeline vibration. Besides, the flow characteristics have been greatly improved.

scholarly journals Analysis and Research on Flow Characteristics of Hot Water Pipeline System

2021 ◽  
Vol 252 ◽  
pp. 03041
Author(s):  
Hou Yingzhe ◽  
Wu Hao ◽  
Yan Xiaozhe ◽  
Zhu Haoqiang ◽  
Gao Haitao ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Simulation Method ◽  
Hot Water ◽  
Pipeline System ◽  
Pipe System ◽  
Uniformity Coefficient ◽  
Pipe Model ◽  
Pipeline Vibration

Based on the CFD numerical simulation method, a pipe model was established to study the internal flow characteristics of two different specifications of hot water pipe system, and the related information of the flow field was obtained, such as the internal pressure, flow velocity and flow rate. The results showed that the smoother the pipeline transition was, the smaller the velocity uniformity coefficient would be, and the higher flow field uniformity means the smaller pressure and velocity fluctuations. Therefore, the pipeline vibration will be smaller, and the flow characteristics are greatly improved.

scholarly journals Investigation of Hydrodynamic Flow Characteristics in Helical Coils with Ovality and Wrinkles

2021 ◽  
pp. 570-579
Author(s):  
Govindaraj Periasamy ◽  
Senthilkumar Mouleeswaran ◽  
Prabhu Raja Venugopal ◽  
Chellapandi Perumal
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Flow Characteristics ◽  
Rolling Process ◽  
Hydrodynamic Characteristics ◽  
Helical Coil ◽  
Hydrodynamic Behaviour ◽  
Pressure Development ◽  
Helical Coils ◽  
Critical Portion

The forming of helical coils using a rolling process results in geometrical irregularities (wrinkles and ovality) that are likely to influence the hydrodynamic behaviour of the flow field inside the coil in applications such as air generators. In this study, the above behaviour was investigated by experimental and numerical analyses considering the heat exchanger used in dry air generators. In experimental analysis, a three-turn copper helical coil with wrinkles and ovality was investigated to estimate the global hydrodynamic characteristics inside the helical coil. The results were compared with that of the ideal geometry of a coil without wrinkles and ovality. The effect of wrinkles was assessed through friction factor, and the corresponding equivalent surface roughness was found to increase by 5.7 times, owing to the presence of wrinkles in the helical coil. Numerical simulation was conducted to determine the pressure distribution, velocity distribution, and secondary flow inside the helical coil; the results were validated with experimental data. A critical portion of the helical coil with multiple wrinkles was considered for numerical simulation to investigate the localized effects of wrinkles on the flow field behaviour. The analysis in the vicinity of wrinkles revealed negative pressure development during flow, which in turn would cause re-circulation and cavitation that are undesirable.

scholarly journals Coupled Fluid–Solid Numerical Simulation for Flow Field Characteristics and Supporting Performance of Flexible Support Cylindrical Gas Film Seal

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 97
Author(s):  
Junfeng Sun ◽  
Meihong Liu ◽  
Zhen Xu ◽  
Taohong Liao ◽  
Xiangping Hu ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Thickness ◽  
Fluid Dynamic ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
High Rotational Speed ◽  
Flexible Support ◽  
Flow Field Characteristics

A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.

The Optical Fiber Connector Ceramic Insert Core Injection Mold Design

2014 ◽  
Vol 624 ◽  
pp. 712-714
Author(s):  
Pei Yun Ao
Keyword(s):  
Optical Fiber ◽  
Structural Characteristics ◽  
Flow Characteristics ◽  
Powder Injection ◽  
Mold Design ◽  
Injection Mold ◽  
Additive Formulation ◽  
Injection Mold Design ◽  
Optical Fiber Connector ◽  
Ceramic Insert

According to the structural characteristics of optical fiber connector Ceramic insert core, this article analyzed the structure technology of it. Based on Mold wizard module and Pro/Moldsign module. We conducted injection mold design of optical fiber connector ceramic insert core; Put forward the flow characteristics of zirconia powder injection feeding and binder, lubricants and other additive formulation.

Thermo-flow characteristics and air flow field leading of the air-cooled condenser cell in a power plant

2011 ◽  
Vol 54 (9) ◽  
pp. 2475-2482 ◽  
Author(s):  
WanXi Zhang ◽  
LiJun Yang ◽  
XiaoZe Du ◽  
YongPing Yang
Keyword(s):  
Power Plant ◽  
Flow Field ◽  
Air Flow ◽  
Flow Characteristics

Effects of Valve Disc on Flow Characteristics Inside a Swing Check Valve During Opening and Closing Processes

2021 ◽  
Author(s):  
Yi-xiang Xu ◽  
Qiang Ru ◽  
Huai-yu Yao ◽  
Zhi-jiang Jin ◽  
Jin-yuan Qian
Keyword(s):  
Flow Field ◽  
Working Conditions ◽  
Power Plants ◽  
Flow Characteristics ◽  
Check Valve ◽  
Opening Angle ◽  
Piping System ◽  
Total Moment ◽  
Valve Disc ◽  
Opening And Closing

Abstract The check valve is one of the most important devices for safety protection of the piping system in thermal and nuclear power plants. As the key component of the check valve, the valve disc accounts for a major effect on the flow characteristics especially during the opening and closing processes. In this paper, a typical swing check valve is taken as the research object. In order to make a comparative study, three working conditions of 30% THA (Turbine Heat Acceptance), 50% THA and 100% THA are selected. Focusing on the effects of valve disc, how does the valve disc motion interact with the flow field around the valve disc is analyzed with the help of the dynamic mesh technology. The results show that under the combined action of fluid force and gravity, the check valve can be opened and closed quickly. During the opening process, the maximum total moment of the disc appears between 45° ∼ 50° opening angle, and during the closing process the maximum total moment occurs when the disc fully closed. The flow field near the valve disc has similar variation rules with the rotation of the valve disc in the three working conditions, and the pressure near the valve disc reaches the maximum value at the moment of opening and closing. This study can provide some suggestions for the further optimal design of similar swing check valve.

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