Numerical Simulation of the Urine Flow in a Stented Ureter

2006 ◽  
Vol 129 (2) ◽  
pp. 187-192 ◽  
Author(s):  
Jimmy C. K. Tong ◽  
Ephraim M. Sparrow ◽  
John P. Abraham
Keyword(s):  
Numerical Simulation ◽  
Rational Design ◽  
Numerical Solutions ◽  
Simulation Method ◽  
Flow Path ◽  
Urine Flow ◽  
Flow Through ◽  
Pass Through ◽  
First Time ◽  
Bladder Urine

When a stent is implanted in a blocked ureter, the urine passing from the kidney to the bladder must traverse a very complicated flow path. That path consists of two parallel passages, one of which is the bore of the stent and the other is the annular space between the external surface of the stent and the inner wall of the ureter. The flow path is further complicated by the presence of numerous pass-through holes that are deployed along the length of the stent. These holes allow urine to pass between the annulus and the bore. Further complexity in the pattern of the urine flow occurs because the coiled “pig tails,” which hold the stent in place, contain multiple ports for fluid ingress and egress. The fluid flow in a stented ureter has been quantitatively analyzed here for the first time using numerical simulation. The numerical solutions obtained here fully reveal the details of the urine flow throughout the entire stented ureter. It was found that in the absence of blockages, most of the pass-through holes are inactive. Furthermore, only the port in each coiled pig tail that is nearest the stent proper is actively involved in the urine flow. Only in the presence of blockages, which may occur due to encrustation or biofouling, are the numerous pass-through holes activated. The numerical simulations are able to track the urine flow through the pass-through holes as well as adjacent to the blockages. The simulations are also able to provide highly accurate results for the kidney-to-bladder urine flow rate. The simulation method presented here constitutes a powerful new tool for rational design of ureteral stents in the future.

Numerical Simulation of Pyroclastic Flow at Mt. Semeru in 2002

2019 ◽  
Vol 14 (1) ◽  
pp. 116-125
Author(s):  
Makoto Shimomura ◽  
Wilfridus F. S. Banggur ◽  
Agoes Loeqman ◽  
◽  
Keyword(s):  
Numerical Simulation ◽  
Friction Factor ◽  
Pyroclastic Flow ◽  
Sudden Change ◽  
Simulation Method ◽  
Active Volcano ◽  
Flow Path ◽  
Pyroclastic Flows ◽  
Set Up ◽  
The Individual

Mt. Semeru (3676 m asl.) is an active volcano in Indonesia. Mt. Semeru has a specific topography i.e., a large straight scar in its south-east flank. The geometry of the scar is approx. 2 km in length and 300–500 m width. The scar is connected to three major drainage channels: the Kobokan River, the Kembar River, and the Bang River. On December 29, 2002, a pyroclastic flow (PF) with an approximate volume of 3.25 × 106m3was generated and it traveled 9–11 km along the Bang River. This pyroclastic flow was the largest among the ones generated from 2002–2003 eruptions of Mt. Semeru. All prior recorded pyroclastic flows traveled 1–2.5 km along the Kembar channel. Thus, this pyroclastic flow suddenly changed its flow path, and it traveled more than three times longer than its antecedents. To investigate the cause of the sudden change, a simulated reproduction of this pyroclastic flow was carried out by employing the numerical simulation method proposed by Yamashita and Miyamoto (1993). Due to the uncertainty of the volume of each pyroclastic flow and the temporal change of deposition thickness, a total of 12 simulation cases were set up, with variations in the number of sequence events, the duration of inflow at the upper reach of the flow, and the inter-granular friction factor. The simulation results showed that to explain the sudden change in flow path, the Kembar channel, around 3 km from the vent, has to be buried by antecedent pyroclastic flows. Furthermore, the individual volumes of the prior flows must be less than 0.25–1× 106m3, with an inflow duration of less than 1 min. The friction factor must be set to be 0.5. By using the most acceptable case, the simulated pyroclastic flows were in good agreement with observed results. The results implied that careful investigation and continuous monitoring of the area at 1500–2000 m asl. on the south-east flank of Mt. Semeru are important to prepare for future pyroclastic flows.

scholarly journals Mixing in Axial-Flow Compressors: Conclusions Drawn From 3-D Navier-Stokes Analyses and Experiments

1990 ◽  
Author(s):  
J. H. Leylek ◽  
D. C. Wisler
Keyword(s):  
Experimental Data ◽  
Numerical Solutions ◽  
Turbulence Modeling ◽  
Axial Flow ◽  
Separated Flow ◽  
Navier Stokes ◽  
Tracer Gas ◽  
Flow Through ◽  
First Time ◽  
Axial Flow Compressors

Extensive numerical analyses and experiments have been conducted to understand mixing phenomena in multistage, axial-flow compressors. For the first time in the literature the following are documented: detailed 3-D Navier-Stokes solutions, with high-order turbulence modeling, are presented for flow through a compressor vane row at both design and off-design (increased) loading; comparison of these computations with detailed experimental data show excellent agreement at both loading levels; the results are then used to explain important aspects of mixing in compressors. The 3-D analyses show the development of spanwise and cross-passage flows in the stator and the change in location and extent of separated flow regions as loading increases. The numerical solutions support previous interpretations of experimental data obtained on the same blading using the ethylene tracer-gas technique and hot-wire anemometry. These results, plus new tracer-gas data, show that both secondary flow and turbulent diffusion are mechanisms responsible for both spanwise and cross-passage mixing in axial-flow compressors. The relative importance of the two mechanisms depends upon the configuration and loading levels. It appears that using the correct spanwise distributions of time-averaged inlet boundary conditions for 3-D Navier-Stokes computations enables one to explain much of the flow physics for this stator.

scholarly journals Simulation on Powered Effects of BWB at Take-off Condition

2020 ◽  
Vol 38 (2) ◽  
pp. 231-237
Author(s):  
Gang Yu ◽  
Dong Li ◽  
Zeyu Zhang
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Concept Design ◽  
Aerodynamic Forces ◽  
Design Institute ◽  
Power Effect ◽  
Flow Through ◽  
Engine Power

The influence of engine powered effects on aerodynamic characteristics of BWB300, which was designed by the Airplane Concept Design Institute of Northwestern Polytechnical University, at take-off condition was analyzed by using the numerical simulation method. Firstly, the method of using the inlet and exhaust boundary conditions to analyze the powered engine was validated. Then, the engine powered effects on BWB300 aerodynamic characteristics at take-off condition were researched with flow through nacelle and with powered nacelle. The results indicated that though the powered effect changing the value of aerodynamic forces, there was no change in the aerodynamic curve trend. It's recommended that the engine power effect should be considered in numerical simulation by using with powered nacelle to gain more accurate values of aerodynamic forces. Nevertheless, with flow nacelle also could be used to gain some regular results.

scholarly journals The Turbulent Flow over the BARC Rectangular Cylinder: A DNS Study

2021 ◽  
Author(s):  
Alessandro Chiarini ◽  
Maurizio Quadrio
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Finite Differences ◽  
Turbulence Models ◽  
Fine Tuning ◽  
Rectangular Cylinder ◽  
Budget Equation ◽  
Complete Set ◽  
First Time

AbstractA direct numerical simulation (DNS) of the incompressible flow around a rectangular cylinder with chord-to-thickness ratio 5:1 (also known as the BARC benchmark) is presented. The work replicates the first DNS of this kind recently presented by Cimarelli et al. (J Wind Eng Ind Aerodyn 174:39–495, 2018), and intends to contribute to a solid numerical benchmark, albeit at a relatively low value of the Reynolds number. The study differentiates from previous work by using an in-house finite-differences solver instead of the finite-volumes toolbox OpenFOAM, and by employing finer spatial discretization and longer temporal average. The main features of the flow are described, and quantitative differences with the existing results are highlighted. The complete set of terms appearing in the budget equation for the components of the Reynolds stress tensor is provided for the first time. The different regions of the flow where production, redistribution and dissipation of each component take place are identified, and the anisotropic and inhomogeneous nature of the flow is discussed. Such information is valuable for the verification and fine-tuning of turbulence models in this complex separating and reattaching flow.

scholarly journals An Approach to Determine Optimal Bow Configuration of Polar Ships under Combined Ice and Calm-Water Conditions

2021 ◽  
Vol 9 (6) ◽  
pp. 680
Author(s):  
Hui Li ◽  
Yan Feng ◽  
Muk Chen Ong ◽  
Xin Zhao ◽  
Li Zhou
Keyword(s):  
Numerical Simulation ◽  
Water Resistance ◽  
Numerical Technique ◽  
Experimental Studies ◽  
Resistance Index ◽  
Simulation Method ◽  
Present Approach ◽  
Calm Water ◽  
Level Ice ◽  
Ice Resistance

Selecting an optimal bow configuration is critical to the preliminary design of polar ships. This paper proposes an approach to determine the optimal bow of polar ships based on present numerical simulation and available published experimental studies. Unlike conventional methods, the present approach integrates both ice resistance and calm-water resistance with the navigating time. A numerical simulation method of an icebreaking vessel going straight ahead in level ice is developed using SPH (smoothed particle hydrodynamics) numerical technique of LS-DYNA. The present numerical results for the ice resistance in level ice are in satisfactory agreement with the available published experimental data. The bow configurations with superior icebreaking capability are obtained by analyzing the sensitivities due to the buttock angle γ, the frame angle β and the waterline angle α. The calm-water resistance is calculated using FVM (finite volume method). Finally, an overall resistance index devised from the ship resistance in ice/water weighted by their corresponding weighted navigation time is proposed. The present approach can be used for evaluating the integrated resistance performance of the polar ships operating in both a water route and ice route.

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