Detached eddy simulations and tomographic PIV measurements of flows over surface combatant 5415 at straight-ahead and static drift conditions

2021 ◽  
Vol 238 ◽  
pp. 109658
Author(s):  
Shanti Bhushan ◽  
Hyunse Yoon ◽  
Frederick Stern
Keyword(s):  
Piv Measurements ◽  
Tomographic Piv ◽  
Surface Combatant ◽  
Drift Conditions ◽  
Straight Ahead

Scalability studies and large grid computations for surface combatant using CFDShip-Iowa

2011 ◽  
Vol 25 (4) ◽  
pp. 466-487 ◽  
Author(s):  
Shanti Bhushan ◽  
Pablo Carrica ◽  
Jianming Yang ◽  
Frederick Stern
Keyword(s):  
Free Surface ◽  
Message Passing Interface ◽  
Free Surface Flows ◽  
Processing Unit ◽  
Mean Flow ◽  
Time Step ◽  
Vortical Structures ◽  
Cpu Time ◽  
Surface Combatant ◽  
Straight Ahead

Scalability studies and computations using the largest grids to date for free-surface flows are performed using message-passing interface (MPI)-based CFDShip-Iowa toolbox curvilinear (V4) and Cartesian (V6) grid solvers on Navy high-performance computing systems. Both solvers show good strong scalability up to 2048 processors, with V6 showing somewhat better performance than V4. V6 also outperforms V4 in terms of the memory requirements and central processing unit (CPU) time per time-step per grid point. The explicit solvers show better scalability than the implicit solvers, but the latter allows larger time-step sizes, resulting in a lower total CPU time. The multi-grid HYPRE solver shows better scalability than the portable, extensible toolkit for scientific computation solver. The main scalability bottleneck is identified to be the pressure Poisson solver. The memory bandwidth test suggests that further scalability improvements could be obtained by using hybrid MPI/open multi-processing (OpenMP) parallelization. V4-detached eddy simulation (DES) on a 300 M grid for the surface combatant model DTMB 5415 in the straight-ahead condition provides a plausible description of the vortical structures and mean flow patterns observed in the experiments. However, the vortex strengths are over predicted and the turbulence is not resolved. V4-DESs on up to 250 M grids for DTMB 5415 at 20° static drift angle significantly improve the forces and moment predictions compared to the coarse grid unsteady Reynolds averaged Navier–Stokes, due to the improved resolved turbulence predictions. The simulations provide detailed resolution of the free-surface and breaking pattern and vortical and turbulent structures, which will guide planned experiments. V6 simulations on up to 276 M grids for DTMB 5415 in the straight-ahead condition predict diffused vortical structures due to poor wall-layer predictions. This could be due to the limitations of the wall-function implementation for the immersed boundary method.

Portable tomographic PIV measurements of swimming shelled Antarctic pteropods

2016 ◽  
Vol 57 (12) ◽  
Author(s):  
Deepak Adhikari ◽  
Donald R. Webster ◽  
Jeannette Yen
Keyword(s):  
Piv Measurements ◽  
Tomographic Piv

Phase-averaged Tomographic PIV Measurements for a Surface Combatant in Pure Sway Maneuver

2017 ◽  
Author(s):  
Hyunse Yoon ◽  
Frederick Stern
Keyword(s):  
Volume Visualization ◽  
Static Condition ◽  
Core Analysis ◽  
Flow Measurements ◽  
Local Flow ◽  
Tomographic Piv ◽  
Test Conditions ◽  
Uncertainty Estimates ◽  
Surface Combatant ◽  
Similarities And Differences

Forces and moment and phase-averaged Tomographic PIV (TPIV) local flow measurements are performed in a 3 m × 3 m × 100 m towing tank for a 3.048-m long geometrically similar model of surface combatant 5415 in pure sway maneuver. Test conditions are for maximum drift angle 𝛽max = 10° and Froude number Fr = 0.28. The TPIV enables fully volumetric flow measurements and the use of 𝑄-criteria enables vortex volume visualization and core analysis. The objective of the experiment is to extend the knowledge for the static condition vortex separation onset and progression to unsteady dynamic conditions, including integrated CFD. Test conditions meet the IITC criteria for sway frequency and restricted water restrictions. Both the present and previous uncertainty assessment (UA) for forces and moment show acceptable values. The uncertainty estimates for TPIV is done by using a practical approach and the results are comparable with the earlier UA using a conventional approach. Integrated CFD simulations are used to identify flow vortices. The comparison with the previous TPIV results for static maneuver conditions show improvements for the present TPIV using a more advanced algorithm. The pure sway measurements at phases corresponding to straight-ahead and 𝛽max = 10° show similarities and differences with the static maneuver measurements, whereas at intermediate phases substantial vortex interactions and unsteady separation onset and progression is shown. The vortex core analysis shows similarities and differences in the core strength and trajectory with the static drift and dynamic pure yaw maneuvers. The present experiment is ongoing and the initial measurement results and analysis are discussed herein.

scholarly journals Comparing the Aerodynamic Behaviour of Real Footballs to a Smooth Sphere Using Tomographic PIV

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 150
Author(s):  
Matthew Ward ◽  
Martin Passmore ◽  
Adrian Spencer ◽  
Andy Harland ◽  
Henry Hanson ◽  
...  
Keyword(s):  
Particle Image ◽  
Vertical Axis ◽  
Force Balance ◽  
Piv Measurements ◽  
Tomographic Piv ◽  
The Real ◽  
Magnus Effect ◽  
Image Velocimetry ◽  
Insight Into ◽  
Smooth Sphere

Many studies have investigated the forces acting on a football in flight and how these change with the introduction or modification of surface features; however, these rarely give insight into the underlying fluid mechanics causing these changes. In this paper, force balance and tomographic particle image velocimetry (PIV) measurements were taken on a smooth sphere and a real Telstar18 football at a range of airspeeds. This was done under both static and spinning conditions utilizing a lower support through the vertical axis of the ball. It was found that the presence of the seams and texturing on the real ball were enough to cause a change from a reverse Magnus effect on the smooth ball to a conventional Magnus on the real ball in some conditions. The tomographic PIV data showed the traditional horseshoe-shaped wake structure behind the sphere and how this changed with the type of Magnus effect. It was found that the positioning of these vortices compared well with the measured side forces.

Tomographic PIV measurements of flow patterns in a nasal cavity with geometry acquisition

2013 ◽  
Vol 55 (1) ◽  
Author(s):  
Sunghyuk Im ◽  
Go Eun Heo ◽  
Young Jin Jeon ◽  
Hyung Jin Sung ◽  
Sung Kyun Kim
Keyword(s):  
Nasal Cavity ◽  
Flow Patterns ◽  
Piv Measurements ◽  
Tomographic Piv
Sign in / Sign up

Export Citation Format

Share Document