A Simplified Analytical Model for Estimation of the Initial Waterhammer Pressure and Force on a Circular Tube

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Jong Chull Jo ◽  
Jae Jun Jeong ◽  
Frederick J. Moody
Keyword(s):  
Analytical Model ◽  
Sound Speed ◽  
Circular Tube ◽  
Analysis Model ◽  
Dimensional Solution ◽  
Surrounding Water ◽  
Decompression Wave ◽  
Computational Fluid Dynamics Cfd ◽  
Fixed Radius ◽  
Simplified Analysis

Abstract A simplified analytical model is developed for estimating the initial waterhammer pressure and force on a circular tube when a plane decompression wave, parallel to its axis, passes over it. The simplified analysis superimposes the solutions for a plane pressure wave traveling at sound speed in the surrounding water, and two-dimensional solution to the wave equation in cylindrical coordinates, with a nonflow boundary condition across the tube boundary at a fixed radius. The analytical method is compared to the computational fluid dynamics (CFD) approach by applying to predict the initial waterhammer pressure and force on the closest tube to the feedwater nozzle of a geometrically simplified nuclear steam generator (SG) analysis model, caused by a feedwater pipe break (FWPB). As the result, it is found that the simplified analytical model, while not matching results of the CFD calculations with precise accuracy, does confirm the nature of the waterhammer impact pressure loads on the SG tubes.

The Dynamics of a Cantilevered Pipe Aspirating Fluid Studied by Experimental, Numerical and Analytical Methods

2010 ◽  
Author(s):  
Dana Giacobbi ◽  
Stephanie Rinaldi ◽  
Christian Semler ◽  
Michael P. Pai¨doussis
Keyword(s):  
Analytical Model ◽  
Low Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Computational Structural Mechanics ◽  
Cantilevered Pipe ◽  
The Galerkin Method ◽  
Csm Model ◽  
Ocean Mining ◽  
Flow Experiments ◽  
Flow Velocities

This paper investigates the dynamics of a slender, flexible, aspirating cantilevered pipe, ingesting fluid at its free end and conveying it towards its clamped end. The problem is interesting not only from a fundamental perspective, but also because applications exist, notably in ocean mining [1]. First, the need for the present work is demonstrated through a review of previous research into the topic — spanning many years and yielding often contradictory results — most recently concluding that the system loses stability by flutter at relatively low flow velocities [2]. In the current paper, that conclusion is refined and expanded upon by exploring the problem in three ways: experimentally, numerically and analytically. First, air-flow experiments, in which the flow velocity of the fluid was varied and the frequency and amplitude of oscillation of the pipe were measured, were conducted using different elastomer pipes and intake shapes. Second, a fully-coupled Computational Fluid Dynamics (CFD) and Computational Structural Mechanics (CSM) model was developed in ANSYS in order to simulate experiments and corroborate experimental results. Finally, using an analytical approach, the existing linear equation of motion describing the system was significantly improved upon, and then solved via the Galerkin method in order to determine its stability characteristics. Heavily influenced by a CFD analysis, the proposed analytical model is different from previous ones, most notably because of the inclusion of a two-part fluid depressurization at the intake. In general, both the actual and numerical experiments suggest a first-mode loss of stability by flutter at relatively low flow velocities, which agrees with the results from the new analytical model.

scholarly journals Rapid pivot feeding in pipefish: flow effects on prey and evaluation of simple dynamic modelling via computational fluid dynamics

2008 ◽  
Vol 5 (28) ◽  
pp. 1291-1301 ◽  
Author(s):  
Sam Van Wassenbergh ◽  
Peter Aerts
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Analytical Model ◽  
Dynamic Modelling ◽  
Head Rotation ◽  
Theoretical Models ◽  
Cfd Simulations ◽  
Deceleration Phase ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Effects

Most theoretical models of unsteady aquatic movement in organisms assume that including steady-state drag force and added mass approximates the hydrodynamic force exerted on an organism's body. However, animals often perform explosively quick movements where high accelerations are realized in a few milliseconds and are followed closely by rapid decelerations. For such highly unsteady movements, the accuracy of this modelling approach may be limited. This type of movement can be found during pivot feeding in pipefish that abruptly rotate their head and snout towards prey. We used computational fluid dynamics (CFD) to validate a simple analytical model of cranial rotation in pipefish. CFD simulations also allowed us to assess prey displacement by head rotation. CFD showed that the analytical model accurately calculates the forces exerted on the pipefish. Although the initial phase of acceleration changes the flow patterns during the subsequent deceleration phase, the accuracy of the analytical model was not reduced during this deceleration phase. Our analysis also showed that prey are left approximately stationary despite the quickly approaching pipefish snout. This suggests that pivot-feeding fish need little or no suction to compensate for the effects of the flow induced by cranial rotation.

The Analysis of Automotive Door Seal Energy Consumption

2011 ◽  
Vol 80-81 ◽  
pp. 714-718
Author(s):  
Yun Kai Gao ◽  
Da Wei Gao
Keyword(s):  
Energy Consumption ◽  
Elastic Force ◽  
Bernoulli Equation ◽  
Analysis Model ◽  
Damping Force ◽  
Total Energy Consumption ◽  
Linear Elastic ◽  
Non Linear ◽  
Linear Damping ◽  
Simplified Analysis

The seal deformation of automotive door is caused by the door compression forces, including non-linear elastic force and non-linear damping force. The working principles of them are analyzed and a new simplified analysis model is built. Based on the Bernoulli equation and the law of conservation of mass, the mathematical models are established to calculate energy consumption of the seal system. According to the analysis results, the energy consumption of non-linear elastic force and non-linear damping force are respectively 84% and 16% of the total energy consumption of the seal system. At last, the calculation data is compared with the test data and the error is less than 5%, so the calculation method proposed in this paper is observed to be accurate.

Thermohydrodynamic Modeling of a Tapered-Land Thrust Bearing With Validation Against Experimental Data

2021 ◽  
Author(s):  
Seckin Gokaltun
Keyword(s):  
Heat Transfer ◽  
Transfer Problem ◽  
Load Capacity ◽  
Solid Surfaces ◽  
Fluid Film ◽  
Transfer Model ◽  
Analysis Model ◽  
Load Range ◽  
Benchmark Data ◽  
Computational Fluid Dynamics Cfd

Abstract In this work, a computational fluid-film bearing analysis model has been utilized in order to investigate the conjugate heat transfer problem for a tapered-land bearing using computational fluid dynamics (CFD) analysis. The academic model is based on the 2D Reynolds equation for the pressure distribution in the film the 3D energy equation is solved for the the bearing pad and the fluid film; therefore, the lubricant properties such as viscosity and density could be made temperature-dependent. The runner is modeled using a 2D axisymmetric mesh. The current analysis excludes the mechanical or thermal deformations of the bearing and the runner since it was observed that the results for output quantities such as film temperature, film pressure, torque and load capacity were within reasonable agreement with the benchmark data obtained from the experiments for the majority of the speed and load cases studied. Comparisons of modeling results against the benchmark data was obtained for cases ranging from 2000 rpm to 10,000 rpm at loads varying from 1000 N to 8000 N. The importance of proper boundary conditions used in the heat transfer model is emphasized as well as the coupling of heat transfer between the film and the solid surfaces of collar and the bearing is described. The results obtained here yielded that a thermohydrodynamic (THD) model that includes the energy transfer into the structures surrounding the fluid film is sufficient enough to predict the performance of a tapered-land bearing at a wide speed and load range in the case where the runner is thick enough that the effect of deformations on the results can be ignored.

scholarly journals A Coupled, Semi-Numerical Model for Thermal Analysis of Medium Frequency Transformer

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 328 ◽  
Author(s):  
Haonan Tian ◽  
Zhongbao Wei ◽  
Sriram Vaisambhayana ◽  
Madasamy Thevar ◽  
Anshuman Tripathi ◽  
...  
Keyword(s):  
Numerical Model ◽  
Analytical Model ◽  
Electromagnetic Analysis ◽  
Medium Frequency ◽  
Fluid Analysis ◽  
Fluid Behavior ◽  
Proposed Model ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Thermal Fluid Analysis

Medium-frequency (MF) transformer has gained much popularity in power conversion systems. Temperature control is a paramount concern, as the unexpected high temperature declines the safety and life expectancy of transformer. The scrutiny of losses and thermal-fluid behavior are thereby critical for the design of MF transformers. This paper proposes a coupled, semi-numerical model for electromagnetic and thermal-fluid analysis of MF oil natural air natural (ONAN) transformer. An analytical model that is based on spatial distribution of flux density and AC factor is exploited to calculate the system losses, while the thermal-hydraulic behavior is modelled numerically leveraging the computational fluid dynamics (CFD) method. A close-loop iterative framework is formulated by coupling the analytical model-based electromagnetic analysis and CFD-based thermal-fluid analysis to address the temperature dependence. Experiments are performed on two transformer prototypes with different conductor types and physical geometries for validation purpose. Results suggest that the proposed model can accurately model the AC effects, losses, and the temperature rises at different system components. The proposed model is computationally more efficient than the full numerical method but it reserves accurate thermal-hydraulic characterization, thus it is promising for engineering utilization.

Study on Estimation Method for Seismic Safety Margin of 3D Piping System With Degradation: Establishing Elasto-Plastic Analysis Model

2004 ◽  
Author(s):  
Akira Mikami ◽  
Makoto Udagawa ◽  
Hajime Takada
Keyword(s):  
Analytical Model ◽  
Cross Section ◽  
Safety Margin ◽  
Estimation Method ◽  
Piping System ◽  
Analysis Model ◽  
Average Amplitude ◽  
Seismic Safety ◽  
Dynamic Analyses ◽  
Plastic Analysis

The authors have proposed an analytical model by which they can simulate the experimental results of a piping system with full circumferential 48% thinning at an elbow or two elbows. A series of elasto-plastic analyses has been carried out in order to investigate the experimental behavior of the piping system. Dynamic analyses describe the ratcheting behavior and the average amplitude of the opening-closing displacement at elbows relatively well. And then static analyses describe ratcheting and ovaling of the cross section of pipes fairy well.

scholarly journals Macro-Modelling Approach for the In-Plane Cyclic Response of Cold-Formed Steel Partition Walls

2020 ◽  
Vol 10 (22) ◽  
pp. 8163
Author(s):  
Dong-Hyeon Shin ◽  
Hyung-Joon Kim
Keyword(s):  
Analytical Model ◽  
Structural Damage ◽  
Damage Mechanism ◽  
Dissipated Energy ◽  
Analysis Model ◽  
Partition Wall ◽  
Cyclic Response ◽  
Partition Walls ◽  
Cold Formed Steel ◽  
Modelling Approach

Past earthquakes demonstrate that non-structural elements could be vulnerable to a relatively low intensity ground shaking which induces negligible structural damage. The study aims to improve previously developed macro-models of cold-formed steel (CFS) partition walls to properly capture their in-plane cyclic response and damage states of important components in a CFS partition wall under imposed excitation. An effective analytical modelling approach is adopted for a simple modelling procedure and less computational effort. The proposed analysis model of partition walls consisting of several lumped spring elements is verified using direct comparison with two full scale CFS partition wall tests. The analytical and experimental results are compared in terms of force–displacement relations, dissipated energy, and an influential damage mechanism of components consisting of partition walls. The comparison shows that the analytical model well captures the experimental response such as the overall strength and stiffness degradation and pinching behavior. Moreover, the damage mechanism predicted by the analytical model is in good agreement with that observed during the tests.

A Study on the Stability of a Mast Structure for Erecting a Large Crane

2011 ◽  
Vol 110-116 ◽  
pp. 1483-1490
Author(s):  
Hoon Hyung Jung ◽  
Chae Sil Kim
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Structural Analysis ◽  
Analytical Model ◽  
Gantry Crane ◽  
The Finite Element Method ◽  
Analysis Model ◽  
The Stability ◽  
The One ◽  
Two Stages

This paper describes a finite element structural analysis model and determines analysis methods appropriate for determining the stability of the mast of a crane. This analysis model allows various analysis approaches to be applied to the conditions affecting the construction of a large gantry crane in order to ensure the stability of the mast of the crane. The finite element method is used as a way to construct an analytical model that can help ensure the stability of the mast in two stages. The model is used in a two-stage analytical process that takes into account the conditions of the model. In this way, the model can be used to judge the stability of the mast. By allowing variation in the analysis approach used for the crane mast, the analysis model may be changed if the conditions of the one-girder gantry crane require. Designers may apply this method for the active analysis of the stability of a crane mast.

scholarly journals Go Fast With the Flow

2015 ◽  
Vol 137 (05) ◽  
pp. 40-45
Author(s):  
John Martin
Keyword(s):  
Fluid Dynamics ◽  
Cfd Modeling ◽  
Surrounding Water ◽  
Support Teams ◽  
Computer Environment ◽  
World Class ◽  
Computational Fluid Dynamics Cfd ◽  
Complex Fluid ◽  
Fluid Flow Regimes ◽  
Force Data

This article discusses various applications of computational fluid dynamics (CFD) in the field of swimming. Using known physics and fluid dynamics relationships, CFD allows complex fluid flow regimes and geometry to be simulated within a computer environment. The ability to obtain segment-specific fluid force data within a full body stroking model provides enormous amounts of information that would be unobtainable via current empirical testing techniques. CFD software imports a realistic geometry of the athlete, generates the geometry of the surrounding water and air, and meshes these geometries to represent the athlete’s body in its surroundings. For world-class swimmers, the pursuit of a record-breaking performance at the 2016 Rio Olympics may well depend on CFD modeling and other simulations just as much as the athlete's physical ability. Experts see several applications for CFD, as engineers and academics continue their research into swimming, and coaches, athletes, and support teams prep for new competitions and championships, including the 2016 Rio Games. The growth of CFD methodology in swimming will rely on the ability to obtain easy and accurate 3-D kinematics.

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