Work related musculoskeletal disorders among medical laboratory professionals: a narrative review

Work related musculoskeletal disorders are common health problem and increasing cause of disability. Laboratory professionals are unique group of healthcare professionals who play an essential part in diagnosis and therapy planning and often their work is associated with potential health hazards. Objective of current study was to review literature on prevalence of work-related musculoskeletal disorders among medical laboratory professionals. Electronic databases and bibliographies were searched and identified papers evaluated against inclusion criteria. The searching strategy uncovered 13 reports. Total 7 studies were included for the review. A high degree of heterogeneity among studies was observed. The overall prevalence’s ranges from 40-60%. With neck being more prevalent 18-78%. However additional high quality studies are required in this area

REEF3D Wave Generation Interface for Commercial Computational Fluid Dynamics Codes

In recent years, computational fluid dynamics (CFD) developments have shown a trend to combine Reynolds-averaged Navier–Stokes (RANS) CFD simulation with other methods such as wave theories or velocity potential-based numerical wave tanks, in order to reduce to computation costs. This is however not a new approach, and there exists a large amount of literature about domain decomposition techniques describing a two way coupling between the RANS CFD models and other methods. One can also observe an increasing popularity in the use of a less sophisticated technique where different fluid solvers are combined with one-way coupling. In these methods, a predefined solution is provided in the far-field, while a three-dimensional (3D) CFD simulation is applied in a limited zone near the structure. The predefined solution is used to specify the background far-field solution. The published solutions use wave theory or a numerical wave tank where the predefined solution is calculated parallel to the RANS solver. In this way, it is possible to reduce the interpolation inaccuracy and the amount of transferred data to the CFD simulation. The disadvantage of this technique is that the far field solver has to be prepared in order to run in parallel with the CFD solver. Due to the one way coupling, it is possible to predefine this information in tables before the CFD simulation. This technique makes it possible to define a general interface between difference solvers without modifying existing codes. This paper presents such a technique where the predefined solution is stored into files.acceptedVersio

A CFD based 3D Numerical Wave Tank to Investigate Wave Interaction with Rectangular Cylinders

Experimental and Computational Hydraulic

Application of a 6DOF algorithm for the investigation of impulse waves generated due to sub-aerial landslides

Inland water bodies such as lakes, rivers and streams are generally considered safe from extreme wave events. Such inland water bodies are susceptible to extreme wave events due to impact of aerial landslides, where a large mass of land impacts the water at high velocities, resulting in a sudden transfer of momentum to the water body. Similar events can occur due to an underwater landslide as well. The evaluation of such extreme events in inland water bodies and the impact of such extreme waves on the regions adjacent to the water body is essential to assess the safety of the constructions on the banks of the water bodies. The generation of extreme waves due to aerial and sub-aerial landslides depends on several parameters such as the height of fall, the composition of the impacting land mass and the bottom slope of the water body. In this paper, the 6DOF algorithm implemented in the open source Computational Fluid Dy- namics (CFD) model REEF3D is used to simulate the motion of a sliding wedge impacting the water free surface. This is used to represent a sliding landmass impacting water after a landslide event. The wedge is represented using a primitive triangular surface mesh and a ray-tracing algorithm is used to determine the position of the object with respect to the underlying grid. Further, the level set method is then used to represent the solid boundary. The motion of the wedge is obtained by propagating the level set equation. The interaction of the wedge with the free water surface is obtained in a sharp and accurate manner using the level set method for both the water free surface and the solid boundary. REEF3D uses a staggered Cartesian numerical grid with a fifth-order WENO scheme for convection discretisation and a third-order Runge- Kutta scheme for time advancement. With the higher-order methods and the level set method, the model can be used to calculate detailed flow information such as the pressure changes in the water on impact and the associated deformation of the water free surface. The accurate representation of these characteristics is essential for correctly evaluating the height and period of the generated extreme wave and associated properties such as the wave celerity and wave run up on the banks during the extreme event

A fully nonlinear potential flow wave modelling procedure for simulations of offshore sea states with various wave breaking scenarios

An accurate representation of a given sea state is crucial for the study of hydrodynamic loads on offshore structures. It is straightforward to check the quality of the reproduced regular waves in a numerical wave tank (NWT). However, many more parameters need to be considered to ensure the quality of irregular waves. In this paper, a fully non-linear potential flow (FNPF) wave model is used to reproduce irregular sea states with different severity of wave breaking. The numerical model solves the velocity potential from the Laplace equation and the free surface boundary conditions using a finite difference method on a σ-coordinate grid. A comprehensive procedure is introduced to ensure the quality of the reproduced full-scale sea states. The effect of wave spectrum discretisation techniques and breaking wave algorithms are compared for an optimal performance. The evaluation of the simulation results takes into account the kurtosis and the wave crest distribution in addition to the wave spectra. The vertical arrangement of the σ-coordinate grid plays an important role in representing the dispersion relation and a grid optimisation method is explained. The current study provides a working procedure that reproduces high-fidelity irregular sea states with breaking waves in an efficient FNPF NWT.publishedVersio

Reduction of the wave propagation error of a sigma grid based numerical tank using a vertical spacing based on the constant truncation error

acceptedVersio

Representation of 3-h Offshore Short-Crested Wave Field in the Fully Nonlinear Potential Flow Model REEF3D::FNPF

Stochastic wave properties are crucial for the design of offshore structures. Short-crested seas are commonly seen at the sites of offshore structures, especially during storm events. A long time duration is required in order to obtain the statistical properties, which is challenging for numerical simulations. In this scenario, a potential flow solver is ideal due to its computational efficiency. A procedure of reproducing accurate short-crested sea states using the open-source fully nonlinear potential flow model REEF3D::FNPF is presented in the paper. The procedure examines the sensitivity of the resolutions in space and time as well as the arrangements of wave gauge arrays. A narrow band power spectrum and a mildly spreading directional spreading function are simulated, and an equal energy method is used to generate input waves and avoid phase-locking. REEF3D::FNPF solves the Laplace equation together with the boundary conditions using a finite difference method. A sigma grid is used in the vertical direction and the vertical grid clustering follows the principle of constant truncation error. High-order discretization methods are implemented in space and time. Message passing interface is used for high performance computation using multiple processors. Three-hour simulations are performed in full-scale at a hypothetic offshore site with constant water depth. The significant wave height, peak period, kurtosis, skewness and ergodicity are examined in the numerically generated wave field. The stochastic wave properties in the numerical wave tank (NWT) using REEF3D::FNPF match the input wave conditions with high fidelity.acceptedVersio

Numerical and experimental investigation of floating structures in regular waves

In this paper, an experimental and numerical study of a floating object is presented. The incorporation of both experimental and numerical tools for the investigation of a simple floating object provides the opportunity to validate the proposed numerical model in detail. The experiments are performed in the wave flume of the Leibniz Universit¨at Hannover, Germany. The flume is capable of generating high-fidelity waves with a wide range of parameters. The study consists of a free-floating box which is placed in the middle of the flume. A soft mooring line system is attached to the box in order to prevent motion perpendicular to the incoming wave direction. Heave and pitch motion are measured for different wave heights and periods. Additionally, measurements under consideration of mooring are presented. For this purpose, different rope mooring systems are attached to the box, and the motion of the moored-floating body in different wave conditions is analysed. In a second step, numerical simulations of the same setup are presented. The applied numerical tool is the open-source CFD model REEF3D

Large scale CFD modeling of wave propagation into Mehamn harbor

Ocean wave propagations into harbours are large scale phenomena with complex wave transformations. Computational fluid dynamics (CFD) has the advantage of capturing most physics with few assumptions. It has also been successfully applied in marine engineering and coastal engineering. Altogether, CFD is considered to be an ideal tool to analyse the wave propagation at harbours. The most prominent limitation of CFD application is the high requirement of computational resources. However, with increasing computational resources, CFD is becoming an attractive alternative. One of the challenges in large scale CFD simulation is to generate the realistic waves. An extended flat-bottom wave generation zone tends to interrupt the continuity of the sub-sea terrain and introduces unrealistic wave transformations. To locate the wave generation zone far from the topography is one remedy, but it demands more computational resources. Therefore, generating waves over an irregular bottom is of particular interest in CFD simulations. In this paper, the three dimensional large scale numerical simulation of wave propagation into Mehamn harbour is performed with waves generated over an irregular bottom using the open source CFD model REEF3D. The relaxation method is used for the wave generation and absorption. A modified wave generation method considering the local water depths and wave numbers is used in this paper. A study case is performed to demonstrate the effect of the irregular bottom wave generation. Then, the large scale wave propagation into Mehamn harbour is simulated with two different waves generated over the real topography. REEF3D simulates the Mehamn harbour wave propagation by solving Navier-Stokes equations on a staggered grid with the finite difference method. The level-set method is applied to capture the free surface. A fifth-order WENO scheme is applied to the convection terms and a third- order TVD scheme is applied on the transient terms. The topography of the harbour is modelled using the local inverse distance interpolation method. The Mehamn harbour simulations show good wave transformation results and indicate a successful application of wave generation over irregular bottoms