scholarly journals <i>HydrothermalFoam</i> v1.0: a 3-D hydrothermal transport model for natural submarine hydrothermal systems

2020 ◽  
Vol 13 (12) ◽  
pp. 6547-6565
Author(s):  
Zhikui Guo ◽  
Lars Rüpke ◽  
Chunhui Tao
Keyword(s):  
Transport Model ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Pure Water ◽  
Three Dimensional ◽  
Hydrothermal Systems ◽  
Dynamic Simulations ◽  
Flow Models ◽  
Wide Range ◽  
Submarine Hydrothermal Systems

Abstract. Herein, we introduce HydrothermalFoam, a three-dimensional hydro-thermo-transport model designed to resolve fluid flow within submarine hydrothermal circulation systems. HydrothermalFoam has been developed on the OpenFOAM platform, which is a finite-volume-based C++ toolbox for fluid-dynamic simulations and for developing customized numerical models that provides access to state-of-the-art parallelized solvers and to a wide range of pre- and post-processing tools. We have implemented a porous media Darcy flow model with associated boundary conditions designed to facilitate numerical simulations of submarine hydrothermal systems. The current implementation is valid for single-phase fluid states and uses a pure-water equation of state (IAPWS-97). We here present the model formulation; OpenFOAM implementation details; and a sequence of 1-D, 2-D, and 3-D benchmark tests. The source code repository further includes a number of tutorials that can be used as starting points for building specialized hydrothermal flow models. The model is published under the GNU General Public License v3.0.

scholarly journals <i>HydrothermalFoam</i> v1.0: a 3-D hydro-thermo-transport model for natural submarine hydrothermal systems

2020 ◽  
Author(s):  
Zhikui Guo ◽  
Lars Rüpke ◽  
Chunhui Tao
Keyword(s):  
Transport Model ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Pure Water ◽  
Three Dimensional ◽  
Hydrothermal Systems ◽  
Dynamic Simulations ◽  
Flow Models ◽  
Wide Range ◽  
Submarine Hydrothermal Systems

Abstract. Herein, we introduce HydrothermalFoam, a three dimensional hydro-thermo-transport model designed to resolve fluid flow within submarine hydrothermal circulation systems. HydrothermalFoam has been developed on the OpenFOAM platform, which is a Finite Volume based C++ toolbox for fluid-dynamic simulations and for developing customized numerical models that provides access to state-of-the-art parallelized solvers and to a wide range of pre- and post-processing tools. We have implemented a porous media Darcy-flow model with associated boundary conditions designed to facilitate numerical simulations of submarine hydrothermal systems. The current implementation is valid for single-phase fluid states and uses a pure water equation-of-state (IAPWS-97). We here present the model formulation, OpenFOAM implementation details, and a sequence of 1-D, 2-D and 3-D benchmark tests. The source code repository further includes a number of tutorials that can be used as starting points for building specialized hydrothermal flow models. The model is published under the GNU General Public License v3.0.

Propulsive Efficiency of the Underwater Dolphin Kick in Humans

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Alfred von Loebbecke ◽  
Rajat Mittal ◽  
Frank Fish ◽  
Russell Mark
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Underwater Video ◽  
Dynamic Simulations ◽  
Slender Body Theory ◽  
Propulsive Efficiency ◽  
Video Footage ◽  
Wide Range ◽  
Dolphin Kick ◽  
Body Theory

Three-dimensional fully unsteady computational fluid dynamic simulations of five Olympic-level swimmers performing the underwater dolphin kick are used to estimate the swimmer’s propulsive efficiencies. These estimates are compared with those of a cetacean performing the dolphin kick. The geometries of the swimmers and the cetacean are based on laser and CT scans, respectively, and the stroke kinematics is based on underwater video footage. The simulations indicate that the propulsive efficiency for human swimmers varies over a relatively wide range from about 11% to 29%. The efficiency of the cetacean is found to be about 56%, which is significantly higher than the human swimmers. The computed efficiency is found not to correlate with either the slender body theory or with the Strouhal number.

scholarly journals Aeolian Sediment Transport Integration in General Stratigraphic Forward Modeling

2011 ◽  
Vol 2011 ◽  
pp. 1-12
Author(s):  
T. Salles ◽  
C. Griffiths ◽  
C. Dyt
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Transport Model ◽  
Numerical Models ◽  
Three Dimensional ◽  
Transport Processes ◽  
Aeolian Deposits ◽  
Geological Processes ◽  
Wide Range ◽  
Mixed Soils

A large number of numerical models have been developed to simulate the physical processes involved in saltation, and, recently to investigate the interaction between soil vegetation cover and aeolian transport. These models are generally constrained to saltation of monodisperse particles while natural saltation occurs over mixed soils. We present a three-dimensional numerical model of steady-state saltation that can simulate aeolian erosion, transport and deposition for unvegetated mixed soils. Our model simulates the motion of saltating particles using a cellular automata algorithm. A simple set of rules is used and takes into account an erosion formula, a transport model, a wind exposition function, and an avalanching process. The model is coupled to the stratigraphic forward model Sedsim that accounts for a larger number of geological processes. The numerical model predicts a wide range of typical dune shapes, which have qualitative correspondence to real systems. The model reproduces the internal structure and composition of the resulting aeolian deposits. It shows the complex formation of dune systems with cross-bedding strata development, bounding surfaces overlaid by fine sediment and inverse grading deposits. We aim to use it to simulate the complex interactions between different sediment transport processes and their resulting geological morphologies.

Optimization of fluid characteristics in the main nozzle of an air-jet loom

2021 ◽  
pp. 004051752110395
Author(s):  
Xinlei Huang ◽  
Lee Michael Clemon ◽  
Mohammad Saidul Islam ◽  
Suvash C. Saha
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Sudden Expansion ◽  
Dynamic Features ◽  
Original Design ◽  
Flow Models ◽  
Air Jet ◽  
Acceleration Tube ◽  
Air Jet Loom ◽  
Fluid Characteristics

As part of the propulsion system, the fluid dynamic features of the main nozzle can immediately affect the stability and efficiency of an air-jet loom. This study aims to optimize the fluid characteristics in the main nozzle of an air-jet loom. To investigate ways of weakening the effect of airflow congestion and backflow phenomenon occurring in the sudden expansion region, the computational fluid dynamics method is employed. Three-dimensional turbulence flow models for a regular main nozzle and 12 prototypes with different nozzle core tip geometry are built, simulated, and analyzed to get the optimum performance. Furthermore, a set of modified equations that consider the direction of airflow are proposed for better estimation of the friction force applied by the nozzle. The result shows that the nozzle core tip's geometry has a significant influence on the internal airflow, affecting the acceleration tube airflow velocity, turbulence intensity, and backflow strength of the sudden expansion region, and other critical fluid characteristics as well. Several proposed models have succeeded in reducing the backflow and outperforming the original design in many different aspects. Models A-60 and C-P, in particular, manage to increase the propulsion force by 37.6% and 20.2% in the acceleration tube while reducing the maximum backflow by 57.1% and 52.2%, respectively. These simulation results can provide invaluable information for the future optimization of the main nozzle.

Investigation of the Flow Field on a Transonic Turbine Nozzle Guide Vane With Rim Seal Cavity Flow Ejection

2009 ◽  
Author(s):  
M. Pau ◽  
G. Paniagua
Keyword(s):  
Flow Field ◽  
Static Pressure ◽  
Numerical Study ◽  
Guide Vane ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Cavity Flow ◽  
Trailing Edge ◽  
Dynamic Simulations ◽  
Purge Flow

Ensuring an adequate life of high pressure turbines requires efficient cooling methods, such as rim seal flow ejection from the stator-rotor wheel space cavity interface, which prevents hot gas ingress into the rotor disk. The present work addresses the potential to improve the efficiency in transonic turbines at certain rim seal ejection rates. To understand this process a numerical study was carried out combining computational fluid dynamic simulations (CFD) and experiments on a single stage axial test turbine. The three dimensional steady CFD analysis was performed modeling the purge cavity flow ejected downstream of the stator blade row, at three flow regimes, subsonic M2 = 0.73, transonic M2 = 1.12 and supersonic M2 = 1.33. Experimental static pressure measurements were used to calibrate the computational model. The main flow field-purge flow interaction is found to be governed by the vane shock structures at the stator hub. The interaction between the vane shocks at the hub and the purge flow has been studied and quantitatively characterized as function of the purge ejection rate. The ejection of 1% of the core flow from the rim seal cavity leads to an increase of the hub static pressure of approximately 7% at the vane trailing edge. This local reduction of the stator exit Mach number decreases the trailing edge losses in the transonic regime. Finally, a numerically predicted loss breakdown is presented, focusing on the relative importance of the trailing edge losses, boundary layer losses, shock losses and mixing losses, as a function of the purge rate ejected. Contrary to the experience in subsonic turbines, results in a transonic model demonstrate that ejecting purge flow improves the vane efficiency due to the shock structures modification downstream of the stator.

Numerical Models of Wind Effects on Temperature Loaded Object

2017 ◽  
Vol 738 ◽  
pp. 69-78
Author(s):  
Vladimira Michalcova ◽  
Lenka Lausova ◽  
Iveta Skotnicova ◽  
Sergej Kuznetsov
Keyword(s):  
Transport Model ◽  
Numerical Models ◽  
Simulation Models ◽  
Lower Atmosphere ◽  
Small Scale ◽  
Ansys Fluent ◽  
Eddy Simulation ◽  
Wide Range ◽  
Shear Stress Transport Model ◽  
The Difference

Wind climate influencing wind loads on buildings and other structures, as well as the dispersion of pollutants from various surfaces is essentially determined by small-scale motions and processes occurring in the atmospheric boundary layer (ABL). The physical and thermal properties of the underlying surface, in conjunction with the dynamics and thermodynamics of the lower atmosphere influence the distribution of wind velocity in thermally stratified ABL. Atmospheric turbulence is characterized by a high degree of irregularity, three-dimensionality, diffusivity, dissipation, and a wide range of motion scales. This article describes a change of selected turbulent variables in the surroundings of flow around a thermally loaded object. The problem is solved numerically in Ansys Fluent 13.0 software using LES (Large eddy simulation) models as well as the Transition SST (Shear Stress Transport) model that is able to take into account the difference between high and low turbulence at the interface between the wake behind an obstacle and the free stream. The results are mutually compared and verified with experimental measurements in the wind tunnel.

scholarly journals An urban large-eddy-based dispersion model for marginal grid resolutions: CAIRDIO v1.0

2020 ◽  
Author(s):  
Michael Weger ◽  
Oswald Knoth ◽  
Bernd Heinold
Keyword(s):  
Dynamic Models ◽  
Numerical Models ◽  
Dispersion Model ◽  
Fluid Dynamic ◽  
Horizontal Resolution ◽  
Two Phase ◽  
Data Set ◽  
Wide Range ◽  
Large Eddy ◽  
Diffusive Interface

Abstract. The capability for high spatial resolutions is an important feature of accurate numerical models dedicated to simulate the large spatial variability of urban air pollution. On the one hand, the well established mesoscale chemistry transport models have their obvious short-comings attributed to their extensive use of paramterizations. On the other hand, obstacle resolving computational fluid dynamic models, while accurate, still often demand too high computational costs, to be applied on a regular and holistic basis. The major reason for the inflated numerical costs is the required horizontal resolution to meaningfully apply the obstacle discretization, which is most often based on boundary-fitted grids, like e.g. the marker-and-cell method. Here we present a large-eddy-simulation approach that uses diffusive obstacle boundaries, which are derived from a simplified diffusive interface approach for moving obstacles. The diffusive interface approach is well established in two-phase modeling, but to the author’s knowledge has not been applied in urban boundary layer simulations so far. Our dispersion model is capable of representing buildings over a wide range of spatial resolutions, including marginally coarse resolutions inaccessible for standard methods. This opens up a very promising opportunity for application of accurate air quality simulations and forecasts on entire mid-sized city domains. Furthermore, our approach is capable of incorporating the influence of the land orography by the additional optional use of terrain-following coordinates. We validated the dynamic core against a set of numerical benchmarks and a standard high-quality wind-tunnel data set for dispersion-model evaluation.

Three-dimensional numerical simulation of local scour in the vicinity of circular side-by-side bridge piers with ice cover

2020 ◽  
Author(s):  
Mohammad Reza Namaee ◽  
Jueyi Sui ◽  
Yongsheng Wu ◽  
Natalie Linklater
Keyword(s):  
Laboratory Experiments ◽  
Transport Model ◽  
Numerical Models ◽  
Three Dimensional ◽  
Ice Cover ◽  
Local Scour ◽  
Bridge Piers ◽  
Accurate Estimation ◽  
Scour Depth ◽  
Cold Regions

Local scour around piers is one of the primary causes of collapse of bridges that cross rivers. The most severe scouring occurs in cold regions where ice cover significantly changes the velocity profile. Having an accurate estimation of the maximum scour depth around bridge piers, especially in cold regions, is necessary for a safer design of piers. In this study, 3-D numerical models are compared to laboratory experiments to examine the process of local scour around bridge piers with and without smooth and rough ice cover. By using the equation of Meyer-Peter Müller, the sediment transport model is validated to approximate the transport of the sediment particles. Numerical results showed good agreements with experimental observations where the maximum scour depth and Turbulent Kinetic Energy (TKE) around bridge piers were the highest under rough ice cover conditions.

Analysis of Velopharyngeal Functions Using Computational Fluid Dynamics Simulations

2019 ◽  
Vol 128 (8) ◽  
pp. 742-748 ◽  
Author(s):  
Hanyao Huang ◽  
Xu Cheng ◽  
Yang Wang ◽  
Dantong Huang ◽  
Yuhao Wei ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Computational Fluid Dynamic Simulation ◽  
Dynamic Features ◽  
Upper Airways ◽  
Dynamic Simulations ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Objectives: Competent velopharyngeal (VP) function is the basis for normal speech. Understanding how VP structure influences the airflow during speech details is essential to the surgical improvement of pharyngoplasty. In this study, we aimed to illuminate the airflow features corresponding to various VP closure states using computed dynamic simulations. Methods: Three-dimensional models of the upper airways were established based on computed tomography of 8 volunteers. The velopharyngeal port was simulated by a cylinder. Computational fluid dynamics simulations were applied to illustrate the correlation between the VP port size and the airflow parameters, including the flow velocity, pressure in the velopharyngeal port, as well as the pressure in oral and nasal cavity. Results: The airflow dynamics at the velopharynx were maintained in the same velopharyngeal pattern as the area of the velopharyngeal port increased from 0 to 25 mm2. A total of 5 airflow patterns with distinct features were captured, corresponding to adequate closure, adequate/borderline closure (Class I and II), borderline/inadequate closure, and inadequate closure. The maximal orifice area that could be tolerated for adequate VP closure was determined to be 2.01 mm2. Conclusion: Different VP functions are of characteristic airflow dynamic features. Computational fluid dynamic simulation is of application potential in individualized VP surgery planning.

scholarly journals The total cavopulmonary connection resistance: a significant impact on single ventricle hemodynamics at rest and exercise

2008 ◽  
Vol 295 (6) ◽  
pp. H2427-H2435 ◽  
Author(s):  
Kartik S. Sundareswaran ◽  
Kerem Pekkan ◽  
Lakshmi P. Dasi ◽  
Kevin Whitehead ◽  
Shiva Sharma ◽  
...  
Keyword(s):  
Heart Rate ◽  
Single Ventricle ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Lumped Parameter Model ◽  
Total Cavopulmonary Connection ◽  
Dynamic Simulations ◽  
Lumped Parameter ◽  
The Impact ◽  
Cavopulmonary Connection

Little is known about the impact of the total cavopulmonary connection (TCPC) on resting and exercise hemodynamics in a single ventricle (SV) circulation. The aim of this study was to elucidate this mechanism using a lumped parameter model of the SV circulation. Pulmonary vascular resistance (1.96 ± 0.80 WU) and systemic vascular resistances (18.4 ± 7.2 WU) were obtained from catheterization data on 40 patients with a TCPC. TCPC resistances (0.39 ± 0.26 WU) were established using computational fluid dynamic simulations conducted on anatomically accurate three-dimensional models reconstructed from MRI ( n = 16). These parameters were used in a lumped parameter model of the SV circulation to investigate the impact of TCPC resistance on SV hemodynamics under resting and exercise conditions. A biventricular model was used for comparison. For a biventricular circulation, the cardiac output (CO) dependence on TCPC resistance was negligible (sensitivity = −0.064 l·min−1·WU−1) but not for the SV circulation (sensitivity = −0.88 l·min−1·WU−1). The capacity to increase CO with heart rate was also severely reduced for the SV. At a simulated heart rate of 150 beats/min, the SV patient with the highest resistance (1.08 WU) had a significantly lower increase in CO (20.5%) compared with the SV patient with the lowest resistance (50%) and normal circulation (119%). This was due to the increased afterload (+35%) and decreased preload (−12%) associated with the SV circulation. In conclusion, TCPC resistance has a significant impact on resting hemodynamics and the exercise capacity of patients with a SV physiology.

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