scholarly journals Computational Fluid Dynamics as an Indicator of Offending Vessel in Trigeminal Neuralgia and Hemifacial Spasms

2018 ◽  
Vol 32 (3) ◽  
pp. 418-425 ◽  
Author(s):  
Mayur V. Kamath ◽  
Yasuhiro Yamada ◽  
Yoko Kato
Keyword(s):  
Shear Stress ◽  
Statistical Analysis ◽  
Wall Shear Stress ◽  
Trigeminal Neuralgia ◽  
Microvascular Decompression ◽  
Wall Pressure ◽  
Imaging Tool ◽  
Computed Tomography Angiogram ◽  
Wall Shear ◽  
Hemifacial Spasms

Abstract Context: Newer Imaging tool for diagnosing offending vessel in trigeminal neuralgia (TN) and Hemifacial spasms (HFS). Aim: To find out if Computational FluidDynamics (CFD) can correctly predict the offending vessel in HFS and TN & thus improving the outcome of Microvascular Decompression) MVD. Settings and Design: CFD is a relatively new mode of imaging. Its application to indicate offending vessel in TN & HFS was tested. Materials & Methods: Retrospectively we studied 13 consecutive patients operated in 2017 for either HFS or TN. Preoperatively MRI & Computed Tomography Angiogram (CTA) were done and the offending vessel identified along with its point of contact with the concerned nerve. CFD was done using Hemoscope 2015 software and wall pressure, wall shear stress, vector & streamline flow were obtained in the offending vessel (test) & contralateral vessel (control). Results of these were charted on an excel sheet & results analyzed. The postoperativeoutcome were assessed and compared with CFD results. Statistical analysis used: Small study group hence statistical analysis couldn’t be applied. Results: Of the 13 patients, offending artery had high wall pressure in 12 and increased wall shear stress innine. Among the controls six had high wall pressure and only two had high wall shear stress. Conclusion: CFD can be used to determine offending vessel and can predict good outcome following microvascular decompression.

Wall Pressure and Shear Stress Variations in a 90-Deg Bifurcation During Pulsatile Laminar Flow

1991 ◽  
Vol 113 (1) ◽  
pp. 111-115 ◽  
Author(s):  
J. M. Khodadadi
Keyword(s):  
Shear Stress ◽  
Laminar Flow ◽  
Wall Shear Stress ◽  
Cross Sections ◽  
Adverse Pressure Gradient ◽  
Wall Pressure ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Navier Stokes Equation ◽  
Wall Shear

Wall pressure distribution and shear stress fields for pulsatile laminar flow in a 90-degree bifurcation with rectangular cross sections are evaluated using the results of the numerical solution of the Navier-Stokes equation. The extent of the adverse pressure gradient on the bottom wall of the main duct and the upstream wall of the branch closely correlate to the behavior of the two dynamic recirculation zones which are formed on these two walls. Multiple zones of high and low shear stresses at various sites in the bifurcation are observed. The extent of the fluctuations of the maximum and minimum shear stress is identified. Next-to-the-wall laser Doppler anemometer velocity measurements are used to estimate the shear stress distribution on the walls. In general, qualitative agreement between the experimental and computed wall shear stress values is observed. The variation of the wall shear stress in the vicinity of the branch is discussed in light of the highly perturbed flow field.

scholarly journals Phase Averaged Wall Shear Stress, Wall Pressure and Near Wall Velocity Field Measurements in a Whirling Annular Seal

1995 ◽  
Author(s):  
Gerald L. Morrison ◽  
Robert B. Winslow ◽  
H. Davis Thames
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Field Measurements ◽  
Wall Pressure ◽  
Mean Velocity ◽  
Annular Seal ◽  
Mean Pressure ◽  
Wall Shear ◽  
Anemometer System ◽  
Velocity Turbulence

The flow field inside a 50% eccentric whirling annular seal operating at a Reynolds number of 24,000 and a Taylor number of 6,600 has been measured using a 3-D laser Doppler anemometer system. Flush mount pressure and wall shear stress probes have been used to measure the stresses (normal and shear) along the length of the stator. The rotor was mounted eccentrically on the shaft so that the rotor orbit was circular and rotated at the same speed as the shaft (a whirl ratio of 1.0). This paper presents mean pressure, mean wall shear stress magnitude and mean wall shear stress direction distributions along the length of the seal. Phase averaged wall pressure and wall shear stress are presented along with phase averaged mean velocity and turbulence kinetic energy distributions located 0.16c from the stator wall where c is the seal clearance. The relationships between the velocity, turbulence, wall pressure and wall shear stress are very complex and do not follow simple bulk flow predictions.

Hemodynamic Factors at the Distal End-to-Side Anastomosis of a Bypass Graft With Different POS:DOS Flow Ratios

2000 ◽  
Vol 123 (3) ◽  
pp. 270-276 ◽  
Author(s):  
Xue-Mei Li ◽  
Stanley E. Rittgers
Keyword(s):  
Shear Stress ◽  
Statistical Analysis ◽  
Wall Shear Stress ◽  
Intimal Hyperplasia ◽  
Bypass Graft ◽  
Stress Gradient ◽  
Great Influence ◽  
Flow Patterns ◽  
The Mean ◽  
Wall Shear

A pulsatile flow in vitro model of the distal end-to-side anastomosis of an arterial bypass graft was used to examine the effects that different flow ratios between the proximal outlet segment (POS) and the distal outlet segment (DOS) have on the flow patterns and the distributions of hemodynamic factors in the anastomosis. Amberlite particles were tracked by flow visualization to determine overall flow patterns and velocity measurements were made with Laser Doppler anemometry (LDA) to obtain detailed hemodynamic factors along the artery floor and the graft hood regions. These factors included wall shear stress (WSS), spatial wall shear stress gradient (WSSG), and oscillatory index (OSI). Statistical analysis was used to compare these hemodynamic factors between cases having different POS:DOS flow ratios (Case 1—0:100, Case 2—25:75, Case 3—50:50). The results showed that changes in POS:DOS flow ratios had a great influence on the flow patterns in the anastomosis. With an increase in proximal outlet flow, the range of location of the stagnation point along the artery floor decreased, while the extent of flow separation along the graft hood increased. The statistical results showed that there were significant differences p<0.05 for the mean WSS between cases along the graft hood, but no significant differences were detected along the artery floor. There were no significant differences for the spatial WSSG along both the artery floor and the graft hood. However, there were significant differences p<0.05 in the mean OSI between Cases 1 and 2 and between Cases 1 and 3 both along the artery floor and along the graft hood. Comparing these mechanical factors with histological findings of intimal hyperplasia formation obtained by previous canine studies, the results of the statistical analysis suggest that regions exposed to a combination of low mean WSS and high OSI may be most prone to the formation of intimal hyperplasia.

scholarly journals Phase relationships between velocity, wall pressure, and wall shear stress in a forced turbulent boundary layer

2016 ◽  
Author(s):  
Kevin T. Rosenberg ◽  
Subrahmanyam Duvvuri ◽  
Mitul Luhar ◽  
Beverley J. McKeon ◽  
Casey Barnard ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Wall Pressure ◽  
Wall Shear ◽  
Phase Relationships

Phase-Averaged Wall Shear Stress, Wall Pressure, and Near-Wall Velocity Field Measurements in a Whirling Annular Seal

1996 ◽  
Vol 118 (3) ◽  
pp. 590-597
Author(s):  
G. L. Morrison ◽  
R. B. Winslow ◽  
H. D. Thames
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Three Dimensional ◽  
Field Measurements ◽  
Wall Pressure ◽  
Mean Velocity ◽  
Annular Seal ◽  
Mean Pressure ◽  
Wall Shear ◽  
Anemometer System

The flow field inside a 50 percent eccentric whirling annular seal operating at a Reynolds number of 24,000 and a Taylor number of 6600 has been measured using a three-dimensional laser-Doppler anemometer system. Flush mount pressure and wall shear stress probes have been used to measure the stresses (normal and shear) along the length of the stator. The rotor was mounted eccentrically on the shaft so that the rotor orbit was circular and rotated at the same speed as the shaft (a whirl ratio of 1.0). This paper presents mean pressure, mean wall shear stress magnitude, and mean wall shear stress direction distributions along the length of the seal. Phase-averaged wall pressure and wall shear stress are presented along with phase-averaged mean velocity and turbulence kinetic energy distributions located 0.16c from the stator wall, where c is the seal clearance. The relationships between the velocity, turbulence, wall pressure, and wall shear stress are very complex and do not follow simple bulk flow predictions.

Sign in / Sign up

Export Citation Format

Share Document