A Critical Re-analysis of the Series 64 Performance Data

2015 ◽  
Author(s):  
Donald MacPherson
Keyword(s):  
Prediction Model ◽  
High Speed ◽  
Original Work ◽  
Numerical Data ◽  
Computational Prediction ◽  
Test Results ◽  
Data Set ◽  
Family Of Curves ◽  
Resistance Prediction ◽  
Hull Forms

The Series 64 has been an oft-cited resource for the resistance prediction of high-speed transom-stern round-bilge hull forms since publication of Yeh’s paper (1965). Its range of parameters is extensive, making it one of only a few sets of test data for long and slender hulls. In the course of this author’s planned development of a computational prediction model based on the Series 64 data, significant outliers in the expected series family of curves were revealed and it became evident that there were inconsistencies in the relative relationships between hulls in the series. This prompted a re-analysis of the series to identify potentially erroneous test results and conclusions in the original work, so as to remove them from the numerical data set for a proposed computational model.

Computer Aided Resistance Prediction Of High Speed Planing Hull Forms

1994 ◽  
pp. 23-43
Author(s):  
Mohd. Ramzan Mainal
Keyword(s):  
High Speed ◽  
Computational Procedure ◽  
Model Testing ◽  
Experimental Results ◽  
Total Resistance ◽  
Computer Prediction ◽  
Computer Aided ◽  
Tremendous Amount ◽  
Resistance Prediction ◽  
Hull Forms

Planing crafts have been the traditional solution to high speed at sea. However, the limitations on high speed planing hull forms in a seaway have led to a tremendous amount of work currently being carried out on hydrofoils, catamarans and hybrid crafts. Despite these facts, the warship, commercial and pleasure markets still show demands for planing crafts and many new designs appear every year. The objective of this paper is to develop a computational procedure for predicting the total resistance of hard chine planing hull forms, prior to model testing. The computer prediction is later validated with existing experimental results.

CFD Simulation of Resistance of Highspeed Trimaran Hullforms

2015 ◽  
Author(s):  
Changhwan Son ◽  
Prasanta K. Sahoo ◽  
Vaibhav Aribenchi ◽  
Srikanth Asapana
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Accurate Determination ◽  
Cfd Analysis ◽  
Test Results ◽  
Ansys Fluent ◽  
Speed Range ◽  
Calm Water ◽  
Hull Forms

This paper attempts to carry out a CFD analysis on total resistance for trimaran hull forms based on established NPL systematic series which are high-speed round bilge hull forms. The resistance of high-speed trimaran hull forms have been determined using ANSYS FLUENT, a CFD software package. A systematic series of round bilge demi-hulls were generated, and their resistance in calm water were determined by using ANSYS FLUENT to briefly examine nature and degree of reliability of ANSYS FLUENT. The primary aim of this investigation is to determine resistance characteristics of slender round bilge trimaran hull forms in the high-speed range corresponding to Froude numbers up to 1.0. Model test results obtained from the paper Molland et al (1994) have been used to verify the efficacy of the CFD analysis. The results obtained from CFD have shown considerable promise and further analysis need to be carried out for accurate determination of resistance in trimaran configuration.

A Simple Method for Predicting the Maximum Squat of a High-Speed Displacement Ship

2006 ◽  
Vol 43 (03) ◽  
pp. 146-151
Author(s):  
Tim Gourlay
Keyword(s):  
Satisfactory Agreement ◽  
Model Test ◽  
High Speed ◽  
Simple Formula ◽  
Test Results ◽  
Simple Method ◽  
Wide Range ◽  
Speed Range ◽  
Calm Water ◽  
Hull Forms

A simple formula is developed for predicting the maximum squat of a displacement ship as it passes through the transcritical speed range. This is given in terms of a maximum sinkage coefficient, which is almost constant across a wide range of hull forms. Satisfactory agreement is shown with model test results, and it is shown that large stern sinkages in the order of 3 to 6 meters are predicted for frigate and destroyer type hulls in shallow calm water.

Application of Michell’s Integral to High-Speed Round-Bilge Hull Forms

2020 ◽  
Vol 36 (03) ◽  
pp. 189-201
Author(s):  
Du Lin ◽  
Sahoo K. Prasanta ◽  
Hefazi Hamid
Keyword(s):  
Fluid Flow ◽  
Comparative Study ◽  
High Speed ◽  
Estimation Method ◽  
Optimization Techniques ◽  
Absolute Accuracy ◽  
Efficient Design ◽  
Towing Tank ◽  
Resistance Prediction ◽  
Hull Forms

Computational fluid dynamics (CFD) techniques are becoming increasingly popular in analyzing fluid flow problems in almost all branches of engineering, especially in resistance prediction of ships where complex fluid flow exists, although absolute accuracy is still limited. Application of CFD techniques in resistance prediction of ships is no longer new and is being enthusiastically embraced by researchers as can be seen from articles in journals and conference proceedings. Although the towing tank tests provide better absolute accuracy, modification to hull forms is limited, resulting from both practical and financial constraints. In this respect, CFD techniques and theoretical formulations have an added advantage in the sense that rapid modifications to hull forms can be carried out and results can be obtained, so that a comparative study could be made within a few hours. In this way, a naval architect is in a better position to select a hydrodynamically efficient design. Furthermore, robust and fast hydrodynamic computational methods are essential elements of advanced numerical optimization techniques. A good high-speed design should have favorable resistance qualities, so that operational capabilities are not degraded. Innumerable investigations available in the literature enumerate resistance prediction of systematic series of high-speed hull forms. In this article, the results of a comparative study on resistance of high-speed round-bilge hull forms using CFD techniques, theoretical analysis, and experimental results have been presented. The need for better hull forms and the increased interest in resistance performance call for better data and efficient algorithms to be available at the design and optimization stage to obtain the right balance between resistance and other conflicting requirements. This article provides a study of the following. The result of modeling in SHIPFLOW, which uses a combined potential-flow boundary-layer viscous-flow zonal approach. Application of a fast resistance estimation method with the wave-making resistance by Michell’s integral, the friction resistance by International Towing Tank Conference 1957. Application of Michell’s integral to determine the wave resistance of the systematic series models. Comparison between the total resistance coefficients obtained from experimental work, SHPFLOW, and the fast resistance estimation method.

Selection of children with ultra-severe traumatic brain injury for neurosurgical intervention

2019 ◽  
Vol 23 (6) ◽  
pp. 670-679
Author(s):  
Krista Greenan ◽  
Sandra L. Taylor ◽  
Daniel Fulkerson ◽  
Kiarash Shahlaie ◽  
Clayton Gerndt ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Decision Tree ◽  
Prediction Model ◽  
Severe Traumatic Brain Injury ◽  
Pupillary Response ◽  
Data Set ◽  
Robust Model ◽  
Gcs Score ◽  
Combined Data

OBJECTIVEA recent retrospective study of severe traumatic brain injury (TBI) in pediatric patients showed similar outcomes in those with a Glasgow Coma Scale (GCS) score of 3 and those with a score of 4 and reported a favorable long-term outcome in 11.9% of patients. Using decision tree analysis, authors of that study provided criteria to identify patients with a potentially favorable outcome. The authors of the present study sought to validate the previously described decision tree and further inform understanding of the outcomes of children with a GCS score 3 or 4 by using data from multiple institutions and machine learning methods to identify important predictors of outcome.METHODSClinical, radiographic, and outcome data on pediatric TBI patients (age < 18 years) were prospectively collected as part of an institutional TBI registry. Patients with a GCS score of 3 or 4 were selected, and the previously published prediction model was evaluated using this data set. Next, a combined data set that included data from two institutions was used to create a new, more statistically robust model using binomial recursive partitioning to create a decision tree.RESULTSForty-five patients from the institutional TBI registry were included in the present study, as were 67 patients from the previously published data set, for a total of 112 patients in the combined analysis. The previously published prediction model for survival was externally validated and performed only modestly (AUC 0.68, 95% CI 0.47, 0.89). In the combined data set, pupillary response and age were the only predictors retained in the decision tree. Ninety-six percent of patients with bilaterally nonreactive pupils had a poor outcome. If the pupillary response was normal in at least one eye, the outcome subsequently depended on age: 72% of children between 5 months and 6 years old had a favorable outcome, whereas 100% of children younger than 5 months old and 77% of those older than 6 years had poor outcomes. The overall accuracy of the combined prediction model was 90.2% with a sensitivity of 68.4% and specificity of 93.6%.CONCLUSIONSA previously published survival model for severe TBI in children with a low GCS score was externally validated. With a larger data set, however, a simplified and more robust model was developed, and the variables most predictive of outcome were age and pupillary response.

Factors Affecting Driver Injury Severity in the Wrong-Way Crash: Accounting for Potential Heterogeneity in Means and Variances of Random Parameters

2021 ◽  
pp. 036119812110098
Author(s):  
Miao Yu ◽  
Jinxing Shen ◽  
Changxi Ma
Keyword(s):  
High Speed ◽  
Injury Severity ◽  
Unobserved Heterogeneity ◽  
Research Effort ◽  
Random Parameter ◽  
Policy Implications ◽  
Contributing Factors ◽  
Severe Injuries ◽  
Data Set ◽  
Severity Levels

Because of the high percentage of fatalities and severe injuries in wrong-way driving (WWD) crashes, numerous studies have focused on identifying contributing factors to the occurrence of WWD crashes. However, a limited number of research effort has investigated the factors associated with driver injury-severity in WWD crashes. This study intends to bridge the gap using a random parameter logit model with heterogeneity in means and variances approach that can account for the unobserved heterogeneity in the data set. Police-reported crash data collected from 2014 to 2017 in North Carolina are used. Four injury-severity levels are defined: fatal injury, severe injury, possible injury, and no injury. Explanatory variables, including driver characteristics, roadway characteristics, environmental characteristics, and crash characteristics, are used. Estimation results demonstrate that factors, including the involvement of alcohol, rural area, principal arterial, high speed limit (>60 mph), dark-lighted conditions, run-off-road collision, and head-on collision, significantly increase the severity levels in WWD crashes. Several policy implications are designed and recommended based on findings.

scholarly journals Aerodynamics of inclined cylindrical bodies free-flying in a hypersonic flowfield

2021 ◽  
Vol 62 (9) ◽  
Author(s):  
Patrick M. Seltner ◽  
Sebastian Willems ◽  
Ali Gülhan ◽  
Eric C. Stern ◽  
Joseph M. Brock ◽  
...  
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Data ◽  
Static Stability ◽  
Free Flight ◽  
Aerodynamic Coefficients ◽  
Flow Topology ◽  
Motion Data ◽  
Continuous Rotation ◽  
German Aerospace

Abstract The influence of the flight attitude on aerodynamic coefficients and static stability of cylindrical bodies in hypersonic flows is of interest in understanding the re/entry of space debris, meteoroid fragments, launch-vehicle stages and other rotating objects. Experiments were therefore carried out in the hypersonic wind tunnel H2K at the German Aerospace Center (DLR) in Cologne. A free-flight technique was employed in H2K, which enables a continuous rotation of the cylinder without any sting interferences in a broad angular range from 0$$^{\circ }$$ ∘ to 90$$^{\circ }$$ ∘ . A high-speed stereo-tracking technique measured the model motion during free-flight and high-speed schlieren provided documentation of the flow topology. Aerodynamic coefficients were determined in careful post-processing, based on the measured 6-degrees-of-freedom (6DoF) motion data. Numerical simulations by NASA’s flow solvers Cart3D and US3D were performed for comparison purposes. As a result, the experimental and numerical data show a good agreement. The inclination of the cylinder strongly effects both the flowfield and aerodynamic loads. Experiments and simulations with concave cylinders showed marked difference in aerodynamic behavior due to the presence of a shock–shock interaction (SSI) near the middle of the model. Graphic abstract

scholarly journals Evaluating Presence/Absence of Target Microbes in Microbiological Tests

2000 ◽  
Vol 83 (6) ◽  
pp. 1429-1434
Author(s):  
Robert J Blodgett ◽  
Anthony D Hitchins
Keyword(s):  
Performance Studies ◽  
Collaborative Study ◽  
False Negative ◽  
The Other ◽  
Test Results ◽  
Logistic Curve ◽  
Microbiological Method ◽  
Test Portion ◽  
Method Performance ◽  
Data Set

Abstract A typical qualitative microbiological method performance (collaborative) study gathers a data set of responses about a test for the presence or absence of a target microbe. We developed 2 models that estimate false-positive and false-negative rates. One model assumes a constant probability that the tests will indicate the target microbe is present for any positive concentration in the test portion. The other model assumes that this probability follows a logistic curve. Test results from several method performance studies illustrate these estimates.

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