scholarly journals Roughness of a subglacial conduit under Hansbreen, Svalbard

2017 ◽  
Vol 63 (239) ◽  
pp. 423-435 ◽  
Author(s):  
KENNETH D. MANKOFF ◽  
JASON D. GULLEY ◽  
SLAWEK M. TULACZYK ◽  
MATTHEW D. COVINGTON ◽  
XIAOFENG LIU ◽  
...  
Keyword(s):  
Water Pressure ◽  
Geometric Model ◽  
Surface Model ◽  
Hydrological Models ◽  
Cross Sectional ◽  
Large Variability ◽  
Hydraulic Roughness ◽  
Relative Roughness ◽  
Roughness Elements ◽  
Conduit Diameter

ABSTRACTHydraulic roughness exerts an important but poorly understood control on water pressure in subglacial conduits. Where relative roughness values are <5%, hydraulic roughness can be related to relative roughness using empirically-derived equations such as the Colebrook–White equation. General relationships between hydraulic roughness and relative roughness do not exist for relative roughness >5%. Here we report the first quantitative assessment of roughness heights and hydraulic diameters in a subglacial conduit. We measured roughness heights in a 125 m long section of a subglacial conduit using structure-from-motion to produce a digital surface model, and hand-measurements of theb-axis of rocks. We found roughness heights from 0.07 to 0.22 m and cross-sectional areas of 1–2 m2, resulting in relative roughness of 3–12% and >5% for most locations. A simple geometric model of varying conduit diameter shows that when the conduit is small relative roughness is >30% and has large variability. Our results suggest that parameterizations of conduit hydraulic roughness in subglacial hydrological models will remain challenging until hydraulic diameters exceed roughness heights by a factor of 20, or the conduit radius is >1 m for the roughness elements observed here.

Hyperkinetic disorder in a community service for people with intellectual disability

2018 ◽  
pp. 1-5
Author(s):  
Sonn Patel ◽  
Evan Yacoub
Keyword(s):  
Intellectual Disability ◽  
Clinical Sample ◽  
Information Service ◽  
Point Prevalence ◽  
Online Information ◽  
Hyperkinetic Disorder ◽  
Cross Sectional ◽  
Large Variability ◽  
Number Of Patients ◽  
Adults And Children

BackgroundThere appears to be a higher rate of prevalence of hyperkinetic disorder in the intellectual disability (ID) population, although there is a large variability in rates in previous studies. Hyperkinetic disorder can be a challenge to diagnose in a population with ID and can present a barrier to the development of the activities of daily living in an already vulnerable population.ObjectivesOur objective was to examine the point prevalence of hyperkinetic disorder in the ID population in a community ID service and also to determine the prevalence of hyperkinetic disorder based on the level of ID.MethodsA cross-sectional review of the Online Information Service ‘OLIS’ database was undertaken to establish the total number of patients with ID and those with comorbid hyperkinetic disorder. The overall point prevalence and prevalence based on the level of ID was calculated from the collected data.ResultsThe point prevalence of hyperkinetic disorder in the population with ID was similar to that found in studies in the general population at 3.1% in adults and 32.6% in children. When divided by the level of disability, the calculated point prevalence in both adults and children was highest in the population with mild ID and decreased as the level of disability increased.ConclusionThis report contributes to previous research establishing the rates of hyperkinetic disorder in an ID population and establishes the point prevalence of hyperkinetic disorder in individuals diagnosed with ID in a clinical sample.

BIOMECHANICAL MODEL PREDICTING VALUES OF MUSCLE FORCES IN THE SHOULDER GIRDLE DURING ARM ELEVATION

2010 ◽  
Vol 10 (04) ◽  
pp. 643-666 ◽  
Author(s):  
ERIC BERTHONNAUD ◽  
MELISSA MORROW ◽  
GUILLAUME HERZBERG ◽  
KAI-NAN AN ◽  
JOANNES DIMNET
Keyword(s):  
Geometric Modeling ◽  
Geometric Model ◽  
Contractile Element ◽  
Muscle Forces ◽  
Active Muscle ◽  
Cross Sectional ◽  
Shoulder Complex ◽  
Arm Elevation

A three-dimensional (3D) geometric model for predicting muscle forces in the shoulder complex is proposed. The model was applied throughout the range of arm elevation in the scapular plan. In vitro testing has been performed on 13 cadaveric shoulders. The objectives were to determine homogeneous values of physiological parameters of shoulder muscles and to locate sites of muscular attachment to any bone of the shoulder complex. Muscular fiber lengths, lengths of contractile element (CE), and muscle volumes were measured, corresponding physiological cross-sectional area (PCSA) were calculated, and force/length muscle relations were found. An in vivo biplanar radiography was performed on five volunteers. The photogrammetric reconstruction of bone axes and landmarks were coupled with a geometric modeling of bones and muscle sites of attachment. Muscular paths were drawn and changes in lengths during movement have been estimated. Directions of muscle forces are the same as that of muscular path at the point of attachment to bone. Magnitudes of muscular forces were found from muscle lengths coupled with force/length relations. Passive forces were directly determined contrary to active muscle forces. A resulting active muscle force is calculated from balancing weight and passive forces at each articular center. Active muscle forces were calculated by distributing the resulting force among active muscles based on the muscular PCSA values.

Anthropometry-Based Surface Modeling of the Human Torso

1994 ◽  
Author(s):  
Peng Li ◽  
Peter R. M. Jones
Keyword(s):  
Human Body ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Human Growth ◽  
Surface Model ◽  
Cross Sectional ◽  
Practical Applications ◽  
Garment Design ◽  
Aided Design ◽  
Reference Body

Abstract There is an increasing need for computerized surface model of the human body in human growth, garment design and ergonomics. However, there is a shortage of three-dimensional (3-D) models of the human body in practical applications. This paper presents a new approach for constructing a 3-D surface model of the human torso using anthropometry. The torso is created by from a reference body of average shape which is represented by a family of cross-sectional curves. The shape and size of the reference body can be modified according to anthropometric data. This approach has been implemented on a personal computer. The resulting 3-D model is a parametric surface based on non-uniform B-splines and can easily be exported to other computer aided design applications.

scholarly journals Numerical Investigation of a Hydropower Tunnel: Estimating Localised Head-Loss Using the Manning Equation

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1562 ◽  
Author(s):  
L. Robin Andersson ◽  
J. Gunnar I. Hellström ◽  
Patrik Andreasson ◽  
T. Staffan Lundström
Keyword(s):  
Head Loss ◽  
Water Tunnel ◽  
Hydraulic Radius ◽  
Dominant Effect ◽  
Cross Sectional ◽  
Ansys Cfx ◽  
Roughness Elements ◽  
Future Evaluation ◽  
Sectional Shape ◽  
Icem Cfd

The fluid dynamics within a water tunnel is investigated numerically using a RANS approach with the k- ε turbulence model. The computational model is based on a laser scan of a hydropower tunnel located in Gävunda, Sweden. The tunnel has a typical height of 6.9 m and a width of 7.2 m. While the average cross-sectional shape of the tunnel is smooth the local deviations are significant, where some roughness elements may be in the size of 5 m implying a large variation of the hydraulic radius. The results indicate that the Manning equation can successfully be used to study the localised pressure variations by taking into account the varying hydraulic radius and cross-sectional area of the tunnel. This indicates a dominant effect of the tunnel roughness in connection with the flow, which has the potential to be used in the future evaluation of tunnel durability. ANSYS-CFX was used for the simulations along with ICEM-CFD for building the mesh.

Construction of Analysis-Suitable Vascular Models Using Axis-Aligned Polycubes

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Adam R. Updegrove ◽  
Shawn C. Shadden ◽  
Nathan M. Wilson
Keyword(s):  
Medical Image ◽  
Geometric Model ◽  
Image Data ◽  
Boundary Representation ◽  
Patient Specific ◽  
Surface Model ◽  
Suitable Model ◽  
Computational Domain ◽  
Discrete Surface ◽  
Medical Image Data

Image-based modeling is an active and growing area of biomedical research that utilizes medical imaging to create patient-specific simulations of physiological function. Under this paradigm, anatomical structures are segmented from a volumetric image, creating a geometric model that serves as a computational domain for physics-based modeling. A common application is the segmentation of cardiovascular structures to numerically model blood flow or tissue mechanics. The segmentation of medical image data typically results in a discrete boundary representation (surface mesh) of the segmented structure. However, it is often desirable to have an analytic representation of the model, which facilitates systematic manipulation. For example, the model then becomes easier to union with a medical device, or the geometry can be virtually altered to test or optimize a surgery. Furthermore, to employ increasingly popular isogeometric analysis (IGA) methods, the parameterization must be analysis suitable. Converting a discrete surface model to an analysis-suitable model remains a challenge, especially for complex branched structures commonly encountered in cardiovascular modeling. To address this challenge, we present a framework to convert discrete surface models of vascular geometries derived from medical image data into analysis-suitable nonuniform rational B-splines (NURBS) representation. This is achieved by decomposing the vascular geometry into a polycube structure that can be used to form a globally valid parameterization. We provide several practical examples and demonstrate the accuracy of the methods by quantifying the fidelity of the parameterization with respect to the input geometry.

Automatic Optimisation of Pre-Swirl Nozzle Design

2006 ◽  
Author(s):  
Fabio Ciampoli ◽  
John W. Chew ◽  
Shahrokh Shahpar ◽  
Elisabeth Willocq
Keyword(s):  
Geometric Model ◽  
Stress Constraints ◽  
Hill Climbing ◽  
Surface Model ◽  
Test Case ◽  
Performance Improvements ◽  
Whole Process ◽  
And Performance ◽  
Rsm Model ◽  
Optimisation Methods

The objective of the research described here is to develop and demonstrate use of automatic design methods for pre-swirl nozzles. Performance of pre-swirled cooling air delivery systems depends critically on the design of these nozzles which is subject to manufacturing and stress constraints. The best solution may be a compromise between cost and performance. Here it is shown that automatic optimisation using computational fluid dynamics (CFD) to evaluate nozzle performance can be useful in design. A parametric geometric model of a nozzle with appropriate constraints is first defined and the CFD meshing and solution are then automated. The mesh generation is found to be the most delicate task in the whole process. Direct hill climbing (DHC) and response surface model (RSM) optimisation methods have been evaluated. For the test case considered, significant nozzle performance improvements were obtained using both methods, but the RSM model was preferred.

An effective stress model for creep of clay

1995 ◽  
Vol 32 (5) ◽  
pp. 819-834 ◽  
Author(s):  
Mohammed M. Morsy ◽  
D.H. Chan ◽  
N.R. Morgenstern
Keyword(s):  
Finite Element ◽  
Pore Pressure ◽  
Effective Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Surface Model ◽  
Interpolation Technique ◽  
Stress Integration ◽  
Integration Algorithms ◽  
Double Yield

An effective stress constitutive model to study the problem numerically of creep in the field is presented. A double-yield surface model for the stress–strain–time behaviour of wet clay is described. The model adopts the concept of separating the total deformation into immediate and delayed components. The yield surfaces employed are the modified Cam-clay ellipsoid and the Von Mises cylinder inscribed in the ellipsoid. The proposed numerical scheme incorporates the pore pressure based on field observations into a finite element analysis. An interpolation technique is used to determine the pore pressure at every element. A field example is presented to illustrate the interpolation technique procedure. The scheme not only avoids the complexity of making predictions of pore-water pressure, but also allows the analysis to be carried out in terms of effective stresses based on the actual observed pore pressure. Two stress integration algorithms based on the implicit calculation of plastic strain are implemented and tested for the double-yield surface model. A numerical simulation of stress-controlled drained creep tests confirms the numerical procedure. Key words : constitutive equations, creep, finite element, stress integration algorithms, effective stress approach, pore-water pressure.

Effects of Roughness on Turbulent Flow in Microchannels and Minichannels

2008 ◽  
Author(s):  
Timothy P. Brackbill ◽  
Satish G. Kandlikar
Keyword(s):  
Experimental Study ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Roughness Parameter ◽  
Reynolds Numbers ◽  
Turbulent Regime ◽  
Roughness Effects ◽  
Relative Roughness ◽  
Roughness Elements ◽  
Moody Diagram

The effect of roughness ranging from smooth to 24% relative roughness on laminar flow has been examined in previous works by the authors. It was shown that using a constricted parameter, εFP, the laminar results were predicted well in the roughened channels ([1],[2],[3]). For the turbulent regime, Kandlikar et al. [1] proposed a modified Moody diagram by using the same set of constricted parameters, and using the modification of the Colebrook equation. A new roughness parameter εFP was shown to accurately portray the roughness effects encountered in laminar flow. In addition, a thorough look at defining surface roughness was given in Young et al. [4]. In this paper, the experimental study has been extended to cover the effects of different roughness features on pressure drop in turbulent flow and to verify the validity of the new parameter set in representing the resulting roughness effects. The range of relative roughness covered is from smooth to 10.38% relative roughness, with Reynolds numbers up to 15,000. It was found that using the same constricted parameters some unique characteristics were noted for turbulent flow over sawtooth roughness elements.

scholarly journals Spatio-Temporal Evaluation of Water Storage Trends from Hydrological Models over Australia Using GRACE Mascon Solutions

2020 ◽  
Vol 12 (21) ◽  
pp. 3578
Author(s):  
Xinchun Yang ◽  
Siyuan Tian ◽  
Wei Feng ◽  
Jiangjun Ran ◽  
Wei You ◽  
...  
Keyword(s):  
Land Surface ◽  
Model Development ◽  
Water Storage ◽  
Validation Dataset ◽  
Surface Model ◽  
Hydrological Models ◽  
Infiltration Capacity ◽  
Australian Water ◽  
Community Land Model ◽  
Spatio Temporal

The Gravity Recovery and Climate Experiment (GRACE) data have been extensively used to evaluate the total terrestrial water storage anomalies (TWSA) from hydrological models. However, which individual water storage components (i.e., soil moisture storage anomalies (SMSA) or groundwater water storage anomalies (GWSA)) cause the discrepancies in TWSA between GRACE and hydrological models have not been thoroughly investigated or quantified. In this study, we applied GRACE mass concentration block (mascon) solutions to evaluate the spatio-temporal TWSA trends (2003–2014) from seven prevailing hydrological models (i.e., Noah-3.6, Catchment Land Surface Model (CLSM-F2.5), Variable Infiltration Capacity macroscale model (VIC-4.1.2), Water—Global Assessment and Prognosis (WaterGAP-2.2d), PCRaster Global Water Balance (PCR-GLOBWB-2), Community Land Model (CLM-4.5), and Australian Water Resources Assessment Landscape model (AWRA-L v6)) in Australia and, more importantly, identified which individual water storage components lead to the differences in TWSA trends between GRACE and hydrological models. The results showed that all of the hydrological models employed in this study, except for CLM-4.5 model, underestimated the GRACE-derived TWSA trends. These underestimations can be divided into three categories: (1) ignoring GWSA, e.g., Noah-3.6 and VIC-4.1.2 models; (2) underrating both SMSA and GWSA, e.g., CLSM-F2.5, WaterGAP-2.2d, and PCR-GLOBWB-2 models; (3) deficiently modeling GWSA, e.g., AWRA-L v6 model. In comparison, CLM-4.5 model yielded the best agreement with GRACE but overstated the GRACE-derived TWSA trends due to the overestimation of GWSA. Our results underscore that GRACE mascon solutions can be used as a valuable and efficient validation dataset to evaluate the spatio-temporal performance of hydrological models. Confirming which individual water storage components result in the discrepancies in TWSA between GRACE and hydrological models can better assist in further hydrological model development.

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