Validation of Forced Heave Simulations on a Planing Hull

2021 ◽  
Author(s):  
Nicholas Husser ◽  
Carolyn Judge ◽  
Stefano Brizzolara

Abstract Advances in nonlinear modeling techniques have created opportunities for more robust modeling of planing hull dynamics than previous techniques relying on linear assumptions. These techniques rely on the imposition of complex, coupled forced motions on a hull. RANSE CFD provides a distinct advantage over experimentation when imposing complicated forced motions because mechanical limitations of the forced motion mechanism and uncertainty in the prescribed motion are eliminated, though the accuracy of the simulations needs to be validated. In this work, a series of sinusoidal forced heave experiments on a planing craft are used to validate the force response predicted by simulation for the same forced motion. The accuracy of the predicted force response is evaluated relative to the experiments with the experimental setup uncertainty considered. Within the experimental setup uncertainty, the force response is predicted well by RANSE CFD and is found to be reasonably accurate. The dynamic trim angle is found to have a major impact on the dynamic force response with variations on the order of half a degree having substantial impacts on the measured forces.

1994 ◽  
Vol 116 (2) ◽  
pp. 369-376 ◽  
Author(s):  
G. L. Arauz ◽  
L. San Andres

The effect of a circumferential feeding groove on the dynamic force response of a short length, open end squeeze film damper is studied experimentally. Damper configurations with increasing groove depths and journal orbit radii were tested for several conditions of whirl frequency and lubricant viscosity. Significant levels of dynamic pressure were measured at the circumferential groove, and relatively large tangential (damping) forces are produced at the groove which contribute considerably to the damping characteristics of the SFD test articles. Radial forces of substantial magnitude are determined at the groove and at the thin film land where the squeeze film Reynolds number is typically less than 1. The circumferential groove is thought to induce an inertia like effect into the film land. The experimental results correlate well with the predictions from a groove volume-circumferential flow model developed.


1975 ◽  
Vol 97 (4) ◽  
pp. 1282-1290 ◽  
Author(s):  
John M. Vance ◽  
Alan J. Kirton

An experimental study of the hydrodynamic force response of a squeeze-film bearing damper with end seals was carried out. Measurements of the pressure distribution about a journal constrained to move in a circular orbit were made for the journal orbit centered in the annular clearance and offset from the center of the annular clearance. The effects of cyclic flow in a radial inlet were studied for the case of the journal orbit centered in the annular clearance. For the off-center case the pressure distribution around the damper was measured for four different combinations of eccentricity, radial velocity, and angular velocity of the line of centers, chosen in such a way as to allow calculation of the four bearing coefficients defined by Tondl. The experimentally determined pressure distributions were numerically integrated to determine the force components of the squeeze film. The results are compared to the “long bearing” and the “short bearing” solutions of Reynolds’ equation. For the centered case, good agreement was found with the shape of the “long bearing” solution. Higher-than-predicted pressures and forces for light viscosity oil are explained by showing that this case is operating in the Taylor vortex flow regime. Similar calculations indicate that turbine dampers can also operate with vortex or turbulent flow.


2008 ◽  
Vol 105 (3) ◽  
pp. 977-987 ◽  
Author(s):  
Kirsten Corder ◽  
Ulf Ekelund ◽  
Rebekah M. Steele ◽  
Nicholas J. Wareham ◽  
Søren Brage

Despite much progress with physical activity assessment, the limitations concerning the accurate measurement of physical activity are often amplified in young people due to the cognitive, physiological, and biomechanical changes that occur during natural growth as well as a more intermittent pattern of habitual physical activity in youth compared with adults. This mini-review describes and compares methods to assess habitual physical activity in youth and discusses main issues regarding the use and interpretation of data collected with these techniques. Self-report instruments and movement sensing are currently the most frequently used methods for the assessment of physical activity in epidemiological research; others include heart rate monitoring and multisensor systems. Habitual energy expenditure can be estimated from these input measures with varying degree of uncertainty. Nonlinear modeling techniques, using accelerometry perhaps in combination with physiological parameters like heart rate or temperature, have the greatest potential for increasing the prediction accuracy of habitual physical activity energy expenditure. Although multisensor systems may be more accurate, this must be balanced against feasibility, a balance that shifts with technological and scientific advances and should be considered at the beginning of every new study.


2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Wen-Yu He ◽  
Yang Wang ◽  
Songye Zhu

The shape function-based method is one of the very promising time-domain methods for dynamic force reconstruction, because it can significantly reduce the number of unknowns and shorten the reconstruction time. However, it is challenging to determine the optimum time unit length that can balance the tradeoff between reconstruction accuracy and efficiency in advance. To address this challenge, this paper develops an adaptive dynamic force reconstruction method based on multiscale wavelet shape functions and time-domain deconvolution. A concentrated dynamic force is discretized into units in time domain and the local force in each unit is approximated by wavelet scale functions at an initial scale. Subsequently, the whole response matrix is formulated by assembling the responses induced by the wavelet shape function forces of all time units which are calculated by the structural finite element model (FEM). Then, the wavelet shape function-based force-response equation is established for force reconstruction. Finally, the scale of the force-response equation is lifted by refining the wavelet shape function with high-scale wavelets and dynamic responses with more point data to improve the reconstruction accuracy gradually. Numerical examples of different structural types are analyzed to verify the feasibility and effectiveness of the proposed method.


2011 ◽  
Vol 90-93 ◽  
pp. 3239-3242
Author(s):  
Ming Qiang Xia ◽  
Hong Yu Jia ◽  
Shi Xiong Zheng

Detailed calculation of the dynamic displacement and dynamic internal force response of each structual member of wharf structure in the earthquake are conducted to structural response analysis of finite element numerical model in the Cuntan container wharf under multi-support excitations(MSE). The comparative analysis of results of calculation evaluates the characteristics of the whole dynamic force of the structure , validates and optimizes engineering design and accumulates design experience, simultaneously,in order to further master performance states of container wharf and the application of an advanced type wharf to other regions.


Author(s):  
Chiara Wielgosz ◽  
Anders Rosén ◽  
Raju Datla ◽  
Uihoon Chung ◽  
Jonas Danielsson

This study explores the prospects of using scaled model experiments for capturing the influence of a novel spray deflection concept on planing craft performance in calm water and in waves. An experimental setup with a towed planing craft model is designed and systematic experiments are performed, first with a bare hull model and then with the same model equipped with spray deflectors. Measured trim, sinkage and resistance in calm water and accelerations and resistance in waves are presented. The results, as well as various aspects of the experimental setup and the spray phenomenon, are discussed. The experimental results indicate that the studied spray deflector concept can have positive effects by lowering the resistance as well as the acceleration in waves. The detailed tailoring of the deflectors is concluded to be crucial. The developed experimental setup is concluded to give consistent results that capture the influence of the spray deflection details on the craft resistance and responses and is concluded to be useful for further research as well as for design purposes.


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