Simulation of irregular wave motion using a flap-type wavemaker

The main objective of the present study is to propose a numerical scheme to model irregular wave systems through a Lagrangian, particle-based numerical method, namely, Smoothed Particle Hydrodynamics (SPH). A numerical wave generator tank, which can generate desired irregular waves is modeled by the SPH method. The fluid motion is governed by continuity and Navier-Stokes equations where Weakly Compressible SPH (WCSPH) approximation is employed for the numerical discretization of the problem domain. To generate the irregular wave spectrum, a flap-type wave generator is adopted into the computational domain which yields to the modeling of moving boundary conditions on the problem domain. As benchmark studies, JONSWAP and Pierson-Moskowitz wave spectrums are simulated to validate the obtained wave characteristics with the theoretical results. The performances of the wave maker are tested under different peak wave frequency values. Fast Fourier Transformation (FFT) analysis is conducted to scrutinize the distribution of wave energy spectrum in the frequency domain. In the light of sufficiently long-term simulation results, it can be said that a good agreement is obtained between the numerical and theoretical results, which indicates that the presented SPH scheme can be utilized in further free-surface hydrodynamics studies related to the irregular wave regimes

Diagnostic criteria for early hip osteoarthritis: first steps, based on the CHECK study

Objectives. Although there is a general focus on early diagnosis and treatment of hip OA, there are no validated diagnostic criteria for early-stage hip OA. The current study aimed to take the first steps in developing diagnostic criteria for early-stage hip OA, using factors obtained through history taking, physical examination, radiography and blood testing at the first consultation in individuals presenting with hip pain, suspicious for hip OA, in primary care.Methods. Data of the 543 individuals with 735 symptomatic hips at baseline who had any follow-up data available from the prospective CHECK cohort study were used. A group of 26 clinical experts [general practitioners (GPs), rheumatologists and orthopaedic surgeons] evaluated standardized clinical assessment forms of all subjects on the presence of clinically relevant hip OA 5-10 years after baseline. Using the expert-based diagnoses as reference standard, a backward selection method was used to create predictive models based on pre-defined baseline factors from history taking, physical examination, radiography and blood testing.Results. Prevalence of clinically relevant hip OA during follow-up was 22%. Created models contained four to eight baseline factors (mainly WOMAC pain items, painful/restricted movements and radiographic features) and obtained area under the curve between 0.62 (0.002) and 0.71 (0.002).Conclusion. Based on clinical and radiographic features of hip OA obtained at first consultation at a GP for pain/stiffness of the hip, the prediction of clinically relevant hip OA within 5-10 years was 'poor' to /fair'.Clinical epidemiolog

Association between clinical findings and the presence of lumbar spine osteoarthritis imaging features:A systematic review

OBJECTIVE: Spinal osteoarthritis is difficult to study and diagnose, partly due to the lack of agreed diagnostic criteria. This systematic review aims to give an overview of the associations between clinical and imaging findings suggestive of spinal osteoarthritis in patients with low back pain to make a step towards agreed diagnostic criteria.DESIGN: We searched MEDLINE, Embase, Web of Science, and CINAHL from inception to April 29, 2021 to identify observational studies in adults that assessed the association between selected clinical and imaging findings suggestive of spinal osteoarthritis. Risk of bias was assessed using the Newcastle Ottawa Scale and the quality of evidence was graded using an adaptation of the GRADE approach.RESULTS: After screening 7902 studies, 30 met the inclusion criteria. High-quality evidence was found for the longitudinal association between low back pain (LBP) intensity, and both disc space narrowing and osteophytes, as well as for the association between LBP-related physical functioning and lumbar disc degeneration, the presence of spinal morning stiffness and disc space narrowing and for the lack of association between physical functioning and Schmorl's nodes.CONCLUSIONS: There is high- and moderate-quality evidence of associations between clinical and imaging findings suggestive of spinal osteoarthritis. However, the majority of the studied outcomes had low or very low-quality of evidence. Furthermore, clinical and methodological heterogeneity was a serious limitation, adding to the need and importance of agreed criteria for spinal osteoarthritis, which should be the scope of future research.</p

Self-adaptive approach for optimisation of passive control systems for seismic resistant buildings

The concept of passive control of the seismic response of structures was introduced to improve the performance of structures by increasing their energy dissipation and reduce or eliminate damage in the structural elements. The key task in the design of passive systems is to determine the forces in the control devices (yield/slip or post-tensioning) at each floor, that will result in best performance (e.g. minimum inter-storey drift). This can be achieved by large parametric studies in which both the maximum control force (e.g. at ground level) and the distribution of forces along the height of the structure are varied. Alternatively, optimum forces in the devices can be achieved by semi-active control, where the structure self-adapts to the earthquake. Both solutions are expensive: the first requires hundreds of non-linear response simulations in the design stage; the second needs a system of sensors, controllers and electromechanical devices. Presented here is a new Self Adaptive Optimisation Approach (SAOA) in which the self-optimisation of a semi-active system is used in the design stage and the resulting distribution of control forces is adopted as a passive system. The new approach was evaluated through comparing the simulated dynamic responses of two relatively simple benchmark structures (braced and post-tensioned) with three sets of control forces: (1) passive system with forces obtained in parametric study, (2) semi-active system with self-adapting control forces, and (3) passive system with SAOA-optimized forces. The results show good performance of the SAOA systems, indicating that SAOA offers a simple and effective solution that can replace the existing optimisation approaches for the design of passively controlled earthquake resistant structures. This study presents a novel idea of using the semi-active control as a tool for optimising a passive control system. The passive control systems can be further improved by a larger study in which the semi-active control algorithms are also optimised

On the sph modeling of flow over cylinder beneath to a free-surface

This work aims to model flow around rigid cylinder beneath to a free surface by using a particle based Lagrangian method, namely, Smoothed Particle Hydrodynamics (SPH) which has clear advantages on modeling nonlinear violent free surface problems. This problem which is also regarded as 2-d wave making problem in marine hydrodynamics literature is carried out for three different positions of cylinder centre with two different Froude numbers. The fluid motion is governed by continuity and Eulers equations while Weakly Compressible SPH (WCSPH) approximation together with artificial viscosity term is employed for the numerical discretization of the problem domain. Hybrid Velocity- updated XSPH and Articial Particle Displacement (VXSPH+APD) correction algorithm [1] and standard density correction treatment is also added into the numerical scheme. The Reynolds number is chosen as close to 200 for all cases where three dimensionality first starts to be effective in the flow domain [2]. As the flow characteristics are metastable [12], the free-surface deformations, drag and the lift force on the body shows periodic variation during the evolution of the flow. Free-surface deformations at the maximum and minimum lift instants are compared with the results of Reichl et.al. [12] for the first two cases. The last case considers a higher Froude number and deeper cylinder position where lift and drag forces are compared with the findings of [22]. It is observed that the obtained free-surface profiles, mean values of drag and lift forces give consistent results in a good with the referred literature data

Numerical simulations of multi-phase electro-hydrodynamics flows using a simple incompressible smoothed particle hydrodynamics method

International audienc