This paper presents a new low-cost autonomous underwater vehicle (AUV) for inspection of water-filled tunnels. Deployment in flowing water tunnels and later retrieval at the tunnel exit produces a two-dimensional height vs. time plot of the tunnel, which can be compared to tunnel schematics. The resultant contour data is useful for maintenance planning and tunnel assessment in terms of internal clogging. This paper presents a proof-of-concept for traversing water filled tunnels by using water flow and variable buoyancy. Empirical data is collected in a scaled down version of one specific water supply tunnel in Norway.

Thermoelectrics enables thermal and electrical energy conversion or device cooling without any moving parts. It has remained a significant challenge to manufacture compact and high performance thermoelectric modules in a large volume using the conventional methods because of their drawbacks in practice, such as the long processing time and misalignment of individual thermoelectric elements. Selective laser melting (SLM) based additive manufacturing approach might offer a unique method to fabricate the low cost, reliable, highly efficient, scalable, and environmentally friendly thermoelectric modules. To understand the thermodynamic and hydrodynamic phenomenon during the SLM processing is of critical importance to ensure high quality products. In this paper, we developed a model which can be used to guide the SLM manufacturing of thermoelectric material with other nanoparticles embedded for higher thermoelectric performance. This physical model based on the continuous equations had the ability to analyze the fluid flow driven by buoyancy force and surface tension, which can be used to analyze the influence of the process parameters on the pool size, particle segregation, as well as temperature distribution within the powder bed. This information is very useful for developing robust SLM for thermoelectric device fabrication.

Mooring cable system, fastening the floating platform is an indispensable segment in the development and utilization of ocean energy. However, the nonlinear cable geometry and nonlinear hydrodynamic forces perplex the construction of numerical modelling of mooring cable. Traditionally, the cable modelling is constructed just considering the geometry of cable, the normal, and the tangential directions. Not only the geometry of cable, but also the relative velocity of fluid is involved in constructing of the numerical modelling of cable in this paper. The expression of external loads by this numerical modelling is effective and accurate taking advantage of explicit separation of external loads in transverse and lengthwise directions. This modelling also simplified the formulation of hydrodynamic drag forces which is dominant among external loads. The stiffness and damping of cable, apparent weight, hydrodynamic drag forces, effect of added mass, and Froude-Krylov force are considered during building of this numerical modelling. The mooring cable fastening a floating sphere stands on buoyancy forces due to the submerged sphere. The simulation results of this numerical modelling were compared and verified with the results from ProteusDS which is an offshore simulation code.

In this paper, we advance a methodology for obtaining the statics solution of lumped mass cable system. The method presented here is general enough for most cable configurations (slack or taut), and works well for a broad range of cable elasticity. The forces considered acting on the cable are due to elasticity, weight, buoyancy and aero/hydrodynamics. A shooting method is used to generate the statics solution for the lumped mass model and thus find the equilibrium position of all the cable nodes. This approach converges onto a solution more efficiently compared to other conventional approaches. In particular, for the two-dimensional problem, the solution is obtained from a set of two equations, regardless of how fine the cable discretization is.

The least-squares finite element method (LSFEM), based on minimizing the l 2 -norm of the residual is now well established as a proper approach to deal with the convection dominated fluid dynamic equations. The least-squares finite element method has a number of attractive characteristics such as the lack of an inf-sup condition and the resulting symmetric positive system of algebraic equations unlike Galerkin finite element method (GFEM). However, the higher continuity requirements for second-order terms in the governing equations force the introduction of additional unknowns through the use of an equivalent first-order system of equations or the use of C 1 continuous basis functions. These additional unknowns lead to increased memory and computational requirements that have limited the application of LSFEM to large-scale practical problems. A novel finite element method is proposed that employs a least-squares method for first-order derivatives and a Galerkin method for second order derivatives, thereby avoiding the need for additional unknowns required by a pure LSFEM approach. When the unsteady form of the governing equations is used, a streamline upwinding term is introduced naturally by the least-squares method. Resulting system matrix is always symmetric and positive definite and can be solved by iterative solvers like pre-conditioned conjugate gradient method. The method is stable for convection-dominated flows and allows for equal-order basis functions for both pressure and velocity. The method has been successfully applied here to solve complex buoyancy-driven flow with Boussinesq approximation in a square cavity with differentially heated vertical walls using low-order C 0 continuous elements.

This paper presents preliminary results on the dynamic modelling of a cubic flying robot referred to as the Tryphon. Several Tryphons and other similar cubic flying robots have been built in the course of this project. They are used for artistic performances in museums, art galleries or theatres. Although the Tryphons are functional, they are difficult to control because of limited knowledge of their behaviour. Hence, the development of a dynamic model has the potential to significantly improve the control performances. Based on models found in the literature, the aerostatics, aerodynamics, gravity, buoyancy and inertial effects of the Tryphon are combined into a dynamic model in this paper. The parameters of the proposed model are adjusted based on experimental data obtained with the Tryphons. It is shown that a proper selection and optimization of the parameters can accurately predict the dynamics of the robot. Further extensions of the model are discussed and potential applications are proposed.

Gas vesicles are low-density, gas-filled protein organelles found inside various microorganisms. They have a lipid-free membrane with an average thickness of 2 nm and provide their hosts with buoyancy. In this study we characterized gas vesicle proteins synthesized by the Halobacterium sp. NRC-1 strain making use of molecular modeling methods and molecular dynamics (MD) simulations. The tertiary structure of GvpA protein, the major constituent of the gas vesicle membrane, was predicted using the De Novo computational design method available in the Rosetta Suite 2.3.1 software and was found to be in agreement with experimental data available from previous studies conducted by others and the consensus of different secondary structure prediction web servers. Optimization of the predicted structure was first carried out by energy minimization and simulated annealing. Subsequently, the mechanical properties of GvpA were investigated via constant pressure and temperature (NPT) aqueous MD simulations, in which two approaches were used to study the isothermal compressibility: quantification of the fluctuations in protein volume at constant pressure and temperature, and quantification of the volume changes induced through changes in the simulation pressure. Long term we plan to incorporate this information into multi-scale models of whole gas vesicles.