The Experts below are selected from a list of 4701 Experts worldwide ranked by ideXlab platform

Lynne E Bilston - One of the best experts on this subject based on the ideXlab platform.

  • effect of endoscopic third ventriculostomy on cerebrospinal fluid pressure in the cerebral ventricles
    Journal of Clinical Neuroscience, 2016
    Co-Authors: A Farnoush, Shaokoon Cheng, Lynne E Bilston, Kristy Tan, Lauriane Juge
    Abstract:

    We aimed to show how endoscopic third ventriculostomy (ETV) treatment may affect cerebrospinal fluid (CSF) flow dynamics in hydrocephalus, with and without aqueductal stenosis. Hydrocephalus is a neurological disorder which is characterized by enlarged brain ventricles. The periodic motion of CSF flow as a function of the cardiac cycle was prescribed as the Inlet Boundary Condition at the foramen of Monro, and ETV was modeled as a 5mm diameter hole in the anterior wall of the third ventricle. The results show that ETV reduces the pressure in the ventricles by nine-fold in the model with aqueductal stenosis, and three-fold in the model without aqueductal stenosis. More importantly, ETV changes the temporal characteristics of the CSF pressure waveform in the model without aqueductal stenosis, such that there is higher pressure in the ventricle during diastole. This study suggests that changes in the temporal characteristics of the CSF pressure waveform in the ventricles may be the reason why ETV treatment is not effective for hydrocephalus without aqueductal stenosis.

  • Effect of endoscopic third ventriculostomy on cerebrospinal fluid pressure in the cerebral ventricles
    'Elsevier BV', 2016
    Co-Authors: Farnoush A, Lynne E Bilston, Tan K, Juge L, Cheng S
    Abstract:

    © 2015 Elsevier Ltd. All rights reserved. We aimed to show how endoscopic third ventriculostomy (ETV) treatment may affect cerebrospinal fluid (CSF) flow dynamics in hydrocephalus, with and without aqueductal stenosis. Hydrocephalus is a neurological disorder which is characterized by enlarged brain ventricles. The periodic motion of CSF flow as a function of the cardiac cycle was prescribed as the Inlet Boundary Condition at the foramen of Monro, and ETV was modeled as a 5 mm diameter hole in the anterior wall of the third ventricle. The results show that ETV reduces the pressure in the ventricles by nine-fold in the model with aqueductal stenosis, and three-fold in the model without aqueductal stenosis. More importantly, ETV changes the temporal characteristics of the CSF pressure waveform in the model without aqueductal stenosis, such that there is higher pressure in the ventricle during diastole. This study suggests that changes in the temporal characteristics of the CSF pressure waveform in the ventricles may be the reason why ETV treatment is not effective for hydrocephalus without aqueductal stenosis

  • the effects of the interthalamic adhesion position on cerebrospinal fluid dynamics in the cerebral ventricles
    Journal of Biomechanics, 2010
    Co-Authors: Shaokoon Cheng, Lynne E Bilston
    Abstract:

    The interthalamic adhesion is a unique feature of the third ventricle in the brain. It differs in shape and size and its location varies between individuals. In this study, computational fluid dynamics was performed on 4 three-dimensional models of the cerebral ventricular system with the interthalamic adhesion modeled in different locations in the third ventricle. Cerebrospinal fluid (CSF) was modeled as incompressible Newtonian fluid and flow was assumed laminar. The periodic motion of CSF flow as a function of the cardiac cycle starting from diastole was prescribed as the Inlet Boundary Condition at the foramen of Monroe. Results from this study show how the location of the interthalamic adhesion influences the pattern of pressure distribution in the cerebral ventricles. In addition, the highest CSF pressure in the third ventricle can vary by ∼50% depending on the location of the interthalamic adhesion. We suggest that the interthalamic adhesion may have functional implications on the development of hydrocephalus and it is important to model this anatomical feature in future studies.

A Ricci - One of the best experts on this subject based on the ideXlab platform.

  • simulation of urban Boundary and canopy layer flows in port areas induced by different marine Boundary layer inflow Conditions
    Science of The Total Environment, 2019
    Co-Authors: A Ricci, Massimiliano Burlando, Maria Pia Repetto, Bje Bert Blocken
    Abstract:

    Abstract Computational fluid dynamics (CFD) simulations and wind-tunnel (WT) tests can be considered as Boundary-value problems, where the Inlet Boundary Condition, which is usually obtained inferring Inlet mean wind profiles from on-site measurements or other type of experimental data, represents the large-scale atmospheric forcing exerted at the outer limit of the urban model. It is not clear, however, to which extent the choice of different inflow wind speed profiles may affect WT and CFD results in the urban environment. In the present study, this aspect is investigated through the comparison of the wind flow fields simulated numerically and tested experimentally in an atmospheric Boundary layer wind tunnel (ABLWT) within a district of Livorno city, Italy, called “Quartiere La Venezia”. Three different shapes of inflow profiles were tested using the CFD technique and the results were compared with each other: one is based on the approach-flow profiles measured upstream of the urban model in the WT test section (WT profile) and two are based on anemometric data corresponding to the approach-flow profile measured by means of a LiDAR wind profiler (LiDAR profile 1 and 2). The analysis showed that using different wind speed profiles does not affect significantly the results in the urban canopy layer (UCL), where correlations of 95% and 98% were found between the LiDAR profile 1 and 2 data and the WT profile data (at z = 0.02 m above the bottom), respectively. Conversely, the different inflow profiles strongly affected the results above the UCL. This means that the local-scale effects induced on the wind field in the UCL by the urban texture are dominated mainly by the larger-scale forcing, as within the canopy the flow remains topologically invariant despite the different inflow Conditions.

Bje Bert Blocken - One of the best experts on this subject based on the ideXlab platform.

  • simulation of urban Boundary and canopy layer flows in port areas induced by different marine Boundary layer inflow Conditions
    Science of The Total Environment, 2019
    Co-Authors: A Ricci, Massimiliano Burlando, Maria Pia Repetto, Bje Bert Blocken
    Abstract:

    Abstract Computational fluid dynamics (CFD) simulations and wind-tunnel (WT) tests can be considered as Boundary-value problems, where the Inlet Boundary Condition, which is usually obtained inferring Inlet mean wind profiles from on-site measurements or other type of experimental data, represents the large-scale atmospheric forcing exerted at the outer limit of the urban model. It is not clear, however, to which extent the choice of different inflow wind speed profiles may affect WT and CFD results in the urban environment. In the present study, this aspect is investigated through the comparison of the wind flow fields simulated numerically and tested experimentally in an atmospheric Boundary layer wind tunnel (ABLWT) within a district of Livorno city, Italy, called “Quartiere La Venezia”. Three different shapes of inflow profiles were tested using the CFD technique and the results were compared with each other: one is based on the approach-flow profiles measured upstream of the urban model in the WT test section (WT profile) and two are based on anemometric data corresponding to the approach-flow profile measured by means of a LiDAR wind profiler (LiDAR profile 1 and 2). The analysis showed that using different wind speed profiles does not affect significantly the results in the urban canopy layer (UCL), where correlations of 95% and 98% were found between the LiDAR profile 1 and 2 data and the WT profile data (at z = 0.02 m above the bottom), respectively. Conversely, the different inflow profiles strongly affected the results above the UCL. This means that the local-scale effects induced on the wind field in the UCL by the urban texture are dominated mainly by the larger-scale forcing, as within the canopy the flow remains topologically invariant despite the different inflow Conditions.

Shaokoon Cheng - One of the best experts on this subject based on the ideXlab platform.

  • effect of endoscopic third ventriculostomy on cerebrospinal fluid pressure in the cerebral ventricles
    Journal of Clinical Neuroscience, 2016
    Co-Authors: A Farnoush, Shaokoon Cheng, Lynne E Bilston, Kristy Tan, Lauriane Juge
    Abstract:

    We aimed to show how endoscopic third ventriculostomy (ETV) treatment may affect cerebrospinal fluid (CSF) flow dynamics in hydrocephalus, with and without aqueductal stenosis. Hydrocephalus is a neurological disorder which is characterized by enlarged brain ventricles. The periodic motion of CSF flow as a function of the cardiac cycle was prescribed as the Inlet Boundary Condition at the foramen of Monro, and ETV was modeled as a 5mm diameter hole in the anterior wall of the third ventricle. The results show that ETV reduces the pressure in the ventricles by nine-fold in the model with aqueductal stenosis, and three-fold in the model without aqueductal stenosis. More importantly, ETV changes the temporal characteristics of the CSF pressure waveform in the model without aqueductal stenosis, such that there is higher pressure in the ventricle during diastole. This study suggests that changes in the temporal characteristics of the CSF pressure waveform in the ventricles may be the reason why ETV treatment is not effective for hydrocephalus without aqueductal stenosis.

  • the effects of the interthalamic adhesion position on cerebrospinal fluid dynamics in the cerebral ventricles
    Journal of Biomechanics, 2010
    Co-Authors: Shaokoon Cheng, Lynne E Bilston
    Abstract:

    The interthalamic adhesion is a unique feature of the third ventricle in the brain. It differs in shape and size and its location varies between individuals. In this study, computational fluid dynamics was performed on 4 three-dimensional models of the cerebral ventricular system with the interthalamic adhesion modeled in different locations in the third ventricle. Cerebrospinal fluid (CSF) was modeled as incompressible Newtonian fluid and flow was assumed laminar. The periodic motion of CSF flow as a function of the cardiac cycle starting from diastole was prescribed as the Inlet Boundary Condition at the foramen of Monroe. Results from this study show how the location of the interthalamic adhesion influences the pattern of pressure distribution in the cerebral ventricles. In addition, the highest CSF pressure in the third ventricle can vary by ∼50% depending on the location of the interthalamic adhesion. We suggest that the interthalamic adhesion may have functional implications on the development of hydrocephalus and it is important to model this anatomical feature in future studies.

Chul-hwa Song - One of the best experts on this subject based on the ideXlab platform.

  • turbulent mixing in a rod bundle with vaned spacer grids oecd nea kaeri cfd benchmark exercise test
    Nuclear Engineering and Design, 2014
    Co-Authors: Seokkyu Chang, Seok Jin Kim, Chul-hwa Song
    Abstract:

    Abstract An experimental study titled the 2nd International Benchmark Exercise (IBE-2) has been conducted to provide high-precision data of detailed turbulent flow mixing in a rod bundle for validating the CFD codes being used widely in the nuclear power industry. A 5 × 5 rod bundle having mixing spacer grids was adopted as a test rig, and was contained in a square flow housing with a 170 mm side length and 4670 mm length. The 25 rods in a bundle have dimensions of 25.4 mm in outer diameter and a 3863 mm length. The benchmark experiments have been performed at the MATiS-H water loop facility in KAERI. The axial bulk velocity in a rod bundle was maintained at about 1.50 m/s (equivalent to Re ∼50,000) with loop Conditions of 35 °C and 1.57 bar measured upstream of the spacer during the experiments. Detailed measurements of the turbulent flow in the subchannels were accomplished using 2-D LDA at four different distances (0.5, 1, 4 and 10  D H ) from the downstream of the mixing spacer grid. The upstream flow profiles also have been measured at the Inlet of the mixing spacer grid for the Inlet Boundary Condition. Precise measurements of the lateral and axial velocities in the subchannels are presented at four downstream distances, as well as the Inlet from the mixing spacer grid of two types. Turbulence intensities and vorticities in the subchannels are also evaluated from the velocity measurements.

  • turbulent mixing in a rod bundle with vaned spacer grids oecd nea kaeri cfd benchmark exercise test
    Nuclear Engineering and Design, 2014
    Co-Authors: Seokkyu Chang, Seok Jin Kim, Chul-hwa Song
    Abstract:

    Abstract An experimental study titled the 2nd International Benchmark Exercise (IBE-2) has been conducted to provide high-precision data of detailed turbulent flow mixing in a rod bundle for validating the CFD codes being used widely in the nuclear power industry. A 5 × 5 rod bundle having mixing spacer grids was adopted as a test rig, and was contained in a square flow housing with a 170 mm side length and 4670 mm length. The 25 rods in a bundle have dimensions of 25.4 mm in outer diameter and a 3863 mm length. The benchmark experiments have been performed at the MATiS-H water loop facility in KAERI. The axial bulk velocity in a rod bundle was maintained at about 1.50 m/s (equivalent to Re ∼50,000) with loop Conditions of 35 °C and 1.57 bar measured upstream of the spacer during the experiments. Detailed measurements of the turbulent flow in the subchannels were accomplished using 2-D LDA at four different distances (0.5, 1, 4 and 10  D H ) from the downstream of the mixing spacer grid. The upstream flow profiles also have been measured at the Inlet of the mixing spacer grid for the Inlet Boundary Condition. Precise measurements of the lateral and axial velocities in the subchannels are presented at four downstream distances, as well as the Inlet from the mixing spacer grid of two types. Turbulence intensities and vorticities in the subchannels are also evaluated from the velocity measurements.