VERY DEEP FACILITIES PHYSICAL MODELLING STRATEGIES

1998 ◽  
Vol 38 (1) ◽  
pp. 594
Author(s):  
J B. Hinwood ◽  
A.E. Potts ◽  
P. Sincock
Keyword(s):  
Design Process ◽  
Numerical Models ◽  
Physical Modelling ◽  
Physical Models ◽  
Dynamic Responses ◽  
Laboratory Facilities ◽  
Wide Range ◽  
Final Design ◽  
Modelling Strategies ◽  
Hull Forms

The design process for offshore facilities has used a mix of physical and numerical modelling to provide information on loads and steady dynamic responses in an efficient and accurate fashion. Usually physical modelling is used early in the design process to provide force coefficients for novel forms or novel loading conditions. Physical modelling is also used later in the design process to deal with complex issues for which the available numerical models are not adequate or are inefficient, and it is subsequently used to provide a verification of the final design under a comprehensive set of load cases.All of these applications of physical models remain important in the move to very deep water, but the limitations of water depth, plan area and velocity profile in existing laboratory facilities reduce the capability of physical modelling. At the same time the wide range of novel hull forms, mooring configurations and materials, and riser types increases the requirement for physical data to calibrate the numerical models and increases the need for design validation. Physical modelling procedures, facilities and limitations are discussed and a design methodology is outlined.

scholarly journals Two-Dimensional Numerical Modeling of Flow in Physical Models of Rock Vane and Bendway Weir Configurations

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 458
Author(s):  
Drew C. Baird ◽  
Benjamin Abban ◽  
S. Michael Scurlock ◽  
Steven B. Abt ◽  
Christopher I. Thornton
Keyword(s):  
Numerical Modeling ◽  
Physical Model ◽  
Numerical Models ◽  
Hydraulic Performance ◽  
Physical Models ◽  
Protection Measures ◽  
Design Engineers ◽  
Model Study ◽  
Study Results ◽  
Wide Range

While there are a wide range of design recommendations for using rock vanes and bendway weirs as streambank protection measures, no comprehensive, standard approach is currently available for design engineers to evaluate their hydraulic performance before construction. This study investigates using 2D numerical modeling as an option for predicting the hydraulic performance of rock vane and bendway weir structure designs for streambank protection. We used the Sedimentation and River Hydraulics (SRH)-2D depth-averaged numerical model to simulate flows around rock vane and bendway weir installations that were previously examined as part of a physical model study and that had water surface elevation and velocity observations. Overall, SRH-2D predicted the same general flow patterns as the physical model, but over- and underpredicted the flow velocity in some areas. These over- and underpredictions could be primarily attributed to the assumption of negligible vertical velocities. Nonetheless, the point differences between the predicted and observed velocities generally ranged from 15 to 25%, with some exceptions. The results showed that 2D numerical models could provide adequate insight into the hydraulic performance of rock vanes and bendway weirs. Accordingly, design guidance and implications of the study results are presented for design engineers.

3-D Transient CFD Modeling of Pig Motion

2016 ◽  
Author(s):  
Diego Jaimes Parilli ◽  
Nelson Loaiza ◽  
Janneth García ◽  
Armando Blanco
Keyword(s):  
Pressure Drop ◽  
Numerical Models ◽  
Control Volume ◽  
Physical Models ◽  
Body Motion ◽  
Cfd Modeling ◽  
Maximum Pressure ◽  
Variable Boundary ◽  
Numerical Predictions ◽  
Wide Range

Pigging operations are common procedures for pipeline maintenance. However, questions still remain about pig dynamics due to the difficulties to accurately describe this complex phenomenon. Consequently, most predictions of pig dynamics are based on empirical knowledge deduced from experimental data and numerical models developed considering simplified physical models, without calculate transient pig-flow interaction and neglecting 3D aspect of flow dynamics. Therefore, to present an actual 3D transient model, this paper proposes a novel CFD methodology using a static mesh in a moving control volume. Forces acting on the pig are dynamically computed by a Fluid-Structure Interaction (FSI) approach; pig velocity is obtained for each time instant and it is set as a variable boundary condition. This method was validated with experimental results and it may be used to describe a wide range of rigid body motion immerse in a flow. This approach is then utilized to obtain the transient simulation of a pig launch in a straight water pipeline. Numerical predictions of the static grid method were compared with those obtained using moving mesh simulations. Results show that the pig reaches a terminal velocity higher than average flow velocity and a huge difference on predictions of maximum pressure drop (through the pig) between steady state based models and transient models. Additionally, it was simulated a 2D model to observe the differences between 2D and 3D simulations on the flow characteristics and pig motion features, which shows an important increase of the pressure drop on 3D model over 2D and high pig acceleration in the 3D simulation.

scholarly journals Accuracy of boundary layer treatments at different Reynolds scales

2020 ◽  
Vol 10 (1) ◽  
pp. 295-310
Author(s):  
Nicolás D. Badano ◽  
Angel N. Menéndez
Keyword(s):  
Scale Effects ◽  
Numerical Models ◽  
Physical Models ◽  
Wall Friction ◽  
Navier Stokes ◽  
Parallel Plates ◽  
Scale Free ◽  
Head Losses ◽  
Wide Range ◽  
Resistive Forces

AbstractResistive forces associated to boundary layers (‘friction’) are usually out of scale in physical models of hydraulic structures, especially in the case of hydraulically smooth walls, generating distortions in the model results known as scale effects, that can be problematic in some relevant engineering problems. These scale effects can be quantified and corrected using suitable numerical models. In this paper the accuracy of using numerical simulation through the Reynolds Averaged Navier-Stokes (RANS) approximation in order to represent the head losses introduced by friction in hydraulically smooth walls is evaluated for a wide range of Reynolds scales. This is performed by comparing the numerical results for fully developed flow on circular pipes and between parallel plates against experimental results, using the most popular wall treatments. The associated numerical errors, mesh requirements and ranges of application are established for each treatment. It is shown that, when properly applied, RANS models are able to simulate the head losses produced by smooth wall friction accurately enough as to quantify the scale effects present in physical models. A methodology for upscaling physical model results to prototype scale, free of scale effects, is proposed.

scholarly journals Numerical and Physical Modelling of Wave Overtopping on a Smooth Impermeable Dike with Promenade under Strong Incident Waves

2021 ◽  
Vol 9 (8) ◽  
pp. 865
Author(s):  
Maria Graça Neves ◽  
Eric Didier ◽  
Moisés Brito ◽  
María Clavero
Keyword(s):  
Wave Breaking ◽  
Numerical Models ◽  
Physical Modelling ◽  
Physical Models ◽  
Wave Overtopping ◽  
Mesh Free ◽  
Order Of Magnitude ◽  
Run Up ◽  
Turbulent Models ◽  
Incident Waves

This paper presents a study of run-up/overtopping over a smooth impermeable dike with promenade using 2D and 3D mesh-based and mesh-free numerical models and results from 2D physical modelling for strong energetic incident waves. These waves induce plunging wave breaking and a complex water/air mixture turbulent flow before overtopped the dike, a challenging configuration for numerical models. The analysis is structured in two phases: (i) evaluates the results of 2D numerical and physical models for run-up and overtopping; (ii) compares qualitatively the results of 3D numerical models for overtopping over a dike with promenade between groins located in front of a slope beach. The results indicate that the main differences obtained in run-up and overtopping are due to differences in wave generation and active absorption systems used in physical and numerical models and in turbulent models used by the numerical models. These differences lead to changes on incident wave height and on wave breaking and, consequently, on reflection, run-up and overtopping over the structure. For 3D simulation, even if larger discrepancies were found on overtopping along the dike, mean wave overtopping discharge and water flow height at the crest of the groin head show a similar order of magnitude.

scholarly journals THE NEED FOR PHYSICAL MODELS IN COASTAL ENGINEERING

2018 ◽  
pp. 52
Author(s):  
Edward Couriel ◽  
Lex Nielsen ◽  
Indra Jayewardene ◽  
Bronson McPherson
Keyword(s):  
Numerical Modelling ◽  
Numerical Models ◽  
Physical Modelling ◽  
Coastal Engineering ◽  
Physical Models ◽  
Physical Processes ◽  
Process Understanding ◽  
Coastal Process ◽  
The Cost ◽  
Modelling Methods

Coastal process understanding is based on observations of physical processes in the field and laboratory from which theories are developed. Theories may be expressed mathematically and coded into numerical models. Compared with the cost of field data acquisition and laboratory experiments, the cost of numerical modelling is often perceived to be low. Therefore, there is a tendency to undertake coastal investigation and design using numerical modelling methods alone. However, there is still a need for physical modelling in coastal engineering.

Roles of externalisation activities in the design process

2016 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Maral Babapour Chafi
Keyword(s):  
Design Process ◽  
Design Research ◽  
Research Literature ◽  
Physical Models ◽  
Future Research ◽  
Knowledge Gaps ◽  
Design Processes ◽  
Digital Modelling

Designers engage in various activities, dealing with different materials and media to externalise and represent their form ideas. This paper presents a review of design research literature regarding externalisation activities in design process: sketching, building physical models and digital modelling. The aim has been to review research on the roles of media and representations in design processes, and highlight knowledge gaps and questions for future research.

Identifying Physico-Chemical Laws from the Robotically Collected Data

2019 ◽  
Author(s):  
Liwei Cao ◽  
Danilo Russo ◽  
Vassilios S. Vassiliadis ◽  
Alexei Lapkin
Keyword(s):  
Experimental Data ◽  
Numerical Models ◽  
Predictor Variable ◽  
Physical Models ◽  
Training Data ◽  
Mixed Integer ◽  
Physico Chemical ◽  
Data Points ◽  
Future Work ◽  
The Relationship

<p>A mixed-integer nonlinear programming (MINLP) formulation for symbolic regression was proposed to identify physical models from noisy experimental data. The formulation was tested using numerical models and was found to be more efficient than the previous literature example with respect to the number of predictor variables and training data points. The globally optimal search was extended to identify physical models and to cope with noise in the experimental data predictor variable. The methodology was coupled with the collection of experimental data in an automated fashion, and was proven to be successful in identifying the correct physical models describing the relationship between the shear stress and shear rate for both Newtonian and non-Newtonian fluids, and simple kinetic laws of reactions. Future work will focus on addressing the limitations of the formulation presented in this work, by extending it to be able to address larger complex physical models.</p><p><br></p>

Dynamic analysis of a helical gear reduction by experimental and numerical methods

2020 ◽  
Vol 68 (1) ◽  
pp. 48-58
Author(s):  
Chao Liu ◽  
Zongde Fang ◽  
Fang Guo ◽  
Long Xiang ◽  
Yabin Guan ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Dynamic Analysis ◽  
Dynamic Behavior ◽  
Fourth Order ◽  
Numerical Models ◽  
Helical Gear ◽  
Operating Conditions ◽  
Dynamic Responses ◽  
Lumped Mass ◽  
Gear Mesh

Presented in this study is investigation of dynamic behavior of a helical gear reduction by experimental and numerical methods. A closed-loop test rig is designed to measure vibrations of the example system, and the basic principle as well as relevant signal processing method is introduced. A hybrid user-defined element model is established to predict relative vibration acceleration at the gear mesh in a direction normal to contact surfaces. The other two numerical models are also constructed by lumped mass method and contact FEM to compare with the previous model in terms of dynamic responses of the system. First, the experiment data demonstrate that the loaded transmission error calculated by LTCA method is generally acceptable and that the assumption ignoring the tooth backlash is valid under the conditions of large loads. Second, under the common operating conditions, the system vibrations obtained by the experimental and numerical methods primarily occur at the first fourth-order meshing frequencies and that the maximum vibration amplitude, for each method, appears on the fourth-order meshing frequency. Moreover, root-mean-square (RMS) value of the acceleration increases with the increasing loads. Finally, according to the comparison of the simulation results, the variation tendencies of the RMS value along with input rotational speed agree well and that the frequencies where the resonances occur keep coincident generally. With summaries of merit and demerit, application of each numerical method is suggested for dynamic analysis of cylindrical gear system, which aids designers for desirable dynamic behavior of the system and better solutions to engineering problems.

scholarly journals An Alternative Statistical Model for Predicting Salinity Variations in Estuaries

2020 ◽  
Vol 12 (24) ◽  
pp. 10677
Author(s):  
Ronghui Ye ◽  
Jun Kong ◽  
Chengji Shen ◽  
Jinming Zhang ◽  
Weisheng Zhang
Keyword(s):  
Statistical Model ◽  
River Discharge ◽  
Numerical Models ◽  
Low Cost ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Large River ◽  
Physical Models ◽  
Long Term Effects ◽  
Salinity Variations

Accurate salinity prediction can support the decision-making of water resources management to mitigate the threat of insufficient freshwater supply in densely populated estuaries. Statistical methods are low-cost and less time-consuming compared with numerical models and physical models for predicting estuarine salinity variations. This study proposes an alternative statistical model that can more accurately predict the salinity series in estuaries. The model incorporates an autoregressive model to characterize the memory effect of salinity and includes the changes in salinity driven by river discharge and tides. Furthermore, the Gamma distribution function was introduced to correct the hysteresis effects of river discharge, tides and salinity. Based on fixed corrections of long-term effects, dynamic corrections of short-term effects were added to weaken the hysteresis effects. Real-world model application to the Pearl River Estuary obtained satisfactory agreement between predicted and measured salinity peaks, indicating the accuracy of salinity forecasting. Cross-validation and weekly salinity prediction under small, medium and large river discharges were also conducted to further test the reliability of the model. The statistical model provides a good reference for predicting salinity variations in estuaries.

scholarly journals Design of 3D Additively Manufactured Hybrid Structures for Cranioplasty

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 181
Author(s):  
Roberto De Santis ◽  
Teresa Russo ◽  
Julietta V. Rau ◽  
Ida Papallo ◽  
Massimo Martorelli ◽  
...  
Keyword(s):  
Physical Models ◽  
Cranial Bone ◽  
Head Model ◽  
Rigid Sphere ◽  
Element Analysis ◽  
Aliphatic Polyesters ◽  
Hybrid Device ◽  
Wide Range ◽  
Hybrid Devices ◽  
Technical Solutions

A wide range of materials has been considered to repair cranial defects. In the field of cranioplasty, poly(methyl methacrylate) (PMMA)-based bone cements and modifications through the inclusion of copper doped tricalcium phosphate (Cu-TCP) particles have been already investigated. On the other hand, aliphatic polyesters such as poly(ε-caprolactone) (PCL) and polylactic acid (PLA) have been frequently investigated to make scaffolds for cranial bone regeneration. Accordingly, the aim of the current research was to design and fabricate customized hybrid devices for the repair of large cranial defects integrating the reverse engineering approach with additive manufacturing, The hybrid device consisted of a 3D additive manufactured polyester porous structures infiltrated with PMMA/Cu-TCP (97.5/2.5 w/w) bone cement. Temperature profiles were first evaluated for 3D hybrid devices (PCL/PMMA, PLA/PMMA, PCL/PMMA/Cu-TCP and PLA/PMMA/Cu-TCP). Peak temperatures recorded for hybrid PCL/PMMA and PCL/PMMA/Cu-TCP were significantly lower than those found for the PLA-based ones. Virtual and physical models of customized devices for large cranial defect were developed to assess the feasibility of the proposed technical solutions. A theoretical analysis was preliminarily performed on the entire head model trying to simulate severe impact conditions for people with the customized hybrid device (PCL/PMMA/Cu-TCP) (i.e., a rigid sphere impacting the implant region of the head). Results from finite element analysis (FEA) provided information on the different components of the model.

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