Simplified Transient Numerical Model of a Supersonic Jet Impacting a Substrate

2017 ◽  
Author(s):  
Sichang Xu ◽  
Patrick Pomerleau-Perron ◽  
Gary W. Rankin
Keyword(s):  
Flow Field ◽  
Numerical Solutions ◽  
Transient Flow ◽  
Fluid Dynamic ◽  
Supersonic Jet ◽  
Axially Symmetric ◽  
Rotary Valve ◽  
Time Curve ◽  
Jet Impact ◽  
Impact Region

The transient flow field near the surface of a substrate impacted by a pulsating supersonic jet emerging from a long tube is investigated using a simplified axially symmetric numerical approach. In the system being modeled, the pulses are created using a rotary valve located at the tube entrance. This flow situation approximates the conditions existing in the Shock-Induced Cold Spray process for coating surfaces with metallic particles. Previous numerical studies of transient supersonic jets either focused on jets emerging from orifices or did not give details of the complex supersonic flow field in the jet impact region. The current approximate numerical method considers the flow within the long tube and in the jet impact region. The procedure involves two stages. The upstream pressure variation with time is first determined using a one-dimensional compressible flow approximation of the entire tube and rotary valve arrangement. The resulting pressure versus time curve serves as the transient inlet boundary condition for an axially symmetric computational fluid dynamic solution of the flow through the tube and region of jet impact on the substrate. The numerical solutions of substrate pressure on the jet centerline versus time are compared with available experimental results and predict certain general features of the substrate pressure traces. Although the simplified model is only in fair agreement with some aspects of the experimental curves, it is shown to be useful in explaining certain peculiar flow features. With the aid of the numerical solution, an explanation for the movement and instability of the bow shock wave which forms ahead of the substrate is described.

scholarly journals Computational Fluid Dynamic Analysis of Flow Rate Performance of a Small Piezoelectric-Hydraulic Pump

2021 ◽  
Vol 11 (11) ◽  
pp. 4888
Author(s):  
Phuc Nguyen Anh ◽  
Jae-Sung Bae ◽  
Jai-Hyuk Hwang
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Transient Flow ◽  
Fluid Dynamic ◽  
Check Valve ◽  
Internal Flow ◽  
Pump Efficiency ◽  
Rate Performance ◽  
Hydraulic Pump ◽  
Computational Fluid Dynamic Analysis

This paper investigates the transient flow rate performance of small piezoelectric-hydraulic pumps. In a previous study, a small piezoelectric hydraulic pump was designed and developed to be applicable to the braking systems of small- and medium-sized UAVs (unmanned aerial vehicles). To this end, a thin plate spring check valve was designed in order to effectively discharge the flow in a single direction. The flow rate of the piezoelectric-hydraulic pump is an important criterion for evaluating pump efficiency. Therefore, a study on the parameters affecting such a flow rate is necessary to enhance the efficiency of piezoelectric hydraulic pumps used in brake systems. This study on small piezoelectric-hydraulic pumps is performed to accurately predict the flow rate using a CFD (Computational Fluid Dynamics) tool. In other words, an unsteady CFD method is applied to model the transient flow rate characteristics and the internal flow field of the fluid. The visualization of the internal flow field is evaluated for a better understanding of the flow fields inside the pump. Moreover, this work also illustrates the detailed motion of both the inlet and outlet check valves during the pump operation that fully reflects the phase shift between the check valves and the piston motion, all of which affect the flow rate performance of the pump. An experiment of flow rate characteristics was conducted on a designed piezoelectric-hydraulic pump, which verifies the validity of the CFD results.

Determination of Pump Impeller Deflections: Comparison of FSI-Simulations to Measurements

2006 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen ◽  
Bo Wan
Keyword(s):  
Structural Analysis ◽  
Flow Field ◽  
Transient Flow ◽  
Fluid Dynamic ◽  
Physical Interaction ◽  
Time Step ◽  
Present Contribution ◽  
Pump Impeller ◽  
Pump Rotor

The determination of pump rotor oscillations induced by exciting hydrodynamic forces requires both a solution of the flow field in the pump and an analysis of the structural mechanics of the pump rotor. In the present contribution, simulations which accomplished different coupling methods between the fluid dynamic solution and the structural analysis were carried out for a single-blade pump. In a first approach a one way coupling was used to determine the oscillations of the pump impeller during operation. The forces calculated from the transient flow field were treated as a load acting at the impeller. A comparison of the computed oscillations to measurements showed that in the present case the strong physical interaction between the flow and the impellers structure requires the feedback of the structural analysis to the flow solution to give more meaningful results. In a second approach a simulation was carried out, which accomplished a full coupling of the fluid dynamics and the structural dynamics. Both physics were solved alternating and at least two iterations, one for each physics, were needed to achieve the required coupled response. The calculations were coupled by passing loads across the physics field interfaces. In the present example, for each regarded time step during one impeller revolution, the pressure field acting at the impeller surface was transferred from the CFD solver to the structural solver as the load on the impeller and the computed deflection of the impeller was transferred back deforming the computational grid of the fluid volume.

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.

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.

A new dynamic mesh algorithm for studying the 3D transient flow field of tilting pad journal bearings

2016 ◽  
Vol 230 (12) ◽  
pp. 1470-1482 ◽  
Author(s):  
Mengxuan Li ◽  
Chaohua Gu ◽  
Xiaohong Pan ◽  
Shuiying Zheng ◽  
Qiang Li
Keyword(s):  
Flow Field ◽  
Equilibrium Position ◽  
Transient Flow ◽  
Journal Bearings ◽  
Dynamic Mesh ◽  
Static Equilibrium ◽  
Time Step ◽  
Tilting Pad ◽  
Grid Nodes ◽  
Tilting Pad Journal Bearings

A new dynamic mesh algorithm is developed in this paper to realize the three-dimensional (3D) computational fluid dynamics (CFD) method for studying the small clearance transient flow field of tilting pad journal bearings (TPJBs). It is based on a structured grid, ensuring that the total number and the topology relationship of the grid nodes remain unchanged during the dynamic mesh updating process. The displacements of the grid nodes can be precisely recalculated at every time step. The updated mesh maintains high quality and is suitable for transient calculation of large journal displacement in FLUENT. The calculation results, such as the static equilibrium position and the dynamic characteristic coefficients, are consistent with the two-dimensional (2D) solution of the Reynolds equation. Furthermore, in the process of transient analysis, under conditions in which the journal is away from the static equilibrium position, evident differences appear between linearized and transient oil film forces, indicating that the nonlinear transient calculation is more suitable for studying the rotor-bearing system.

Modeling of Flow Fields of Different Delivery Chamfers in Spray Forming Process

2014 ◽  
Vol 789 ◽  
pp. 554-559
Author(s):  
Yang Liu ◽  
Zhou Li ◽  
Guo Qing Zhang ◽  
Wen Yong Xu
Keyword(s):  
Flow Field ◽  
Gas Flow ◽  
Fluid Dynamic ◽  
Metal Flow ◽  
Spray Forming ◽  
Operating Pressure ◽  
Delivery Tube ◽  
Forming Process ◽  
Atomization Process ◽  
Sharp Point

The computational fluid dynamic (CFD) software was used to calculate the velocity field in atomization chamber of spray forming equipment. The relationship between melt flow rates, gas aspiration of the atomizer and operating pressure are complex, and the above mentioned parameters are closely related to the atomization process. The influences of different delivery chamfers on gas flow field, which is determined by atomizer structure, were analyzed. Using K-epsilon model with a symmetrical domain, the gas dynamic of different delivery chamfer conditions were investigated. The results indicate that the sharp point of delivery tube causes detachment of flow field, and 56°, 45° and 34° chamfer conditions have same diffusion angle. Gas was aspirated from delivery tube when chamfer was 0°, which is beneficial to liquid metal flow in atomization process.

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