Electric Field and Temperature Simulations of High-Voltage Direct Current Cables Considering the Soil Environment

For long distance electric power transport, high-voltage direct current (HVDC) cable systems are a commonly used solution. Space charges accumulate in the HVDC cable insulations due to the applied voltage and the nonlinear electric conductivity of the insulation material. The resulting electric field depends on the material parameters of the surrounding soil environment that may differ locally and have an influence on the temperature distribution in the cable and the environment. To use the radial symmetry of the cable geometry, typical electric field simulations neglect the influence of the surrounding soil, due to different dimensions of the cable and the environment and the resulting high computational effort. Here, the environment and its effect on the resulting electric field is considered and the assumption of a possible radial symmetric temperature within the insulation is analyzed. To reduce the computation time, weakly coupled simulations are performed to compute the temperature and the electric field inside the cable insulation, neglecting insulation losses. The results of a weakly coupled simulation are compared against those of a full transient simulation, considering the insulation losses for two common cable insulations with different maximum operation temperatures. Due to the buried depth of HV cables, an approximately radial symmetric temperature distribution within the insulation is obtained for a single cable and cable pairs when, considering a metallic sheath. Furthermore, the simulations show a temperature increase of the earth–air interface above the buried cable that needs to be considered when computing the cable conductor temperature, using the IEC standards.

Eddy Sensitivity to Jet Characteristics

The atmosphere exhibits two distinct types of jets: the thermally driven subtropical jet and the more poleward eddy-driven jet. Depending on location and season, these jets are often merged or separated, and their position, structure, and intensity strongly influence the eddy fields. Here, the authors study the sensitivity of eddies to changes in the jets’ amplitudes and positions in an idealized general circulation model. A modified Newtonian relaxation scheme that has a very short relaxation time for the mean state and a long relaxation time for eddies is used. This scheme makes it possible to obtain any zonally symmetric temperature distribution and is used to systematically modify the jets’ amplitudes and locations. It is found that eddies are more sensitive to changes in the amplitude of the eddy-driven jet than to changes in the amplitude of the subtropical jet. Furthermore, when the eddy-driven jet is shifted poleward, eddies tend to intensify. These results are tested for robustness in two different reference simulations: one resembling a situation where the subtropical and eddy-driven jets are nearly merged and one when they are separated.

An investigation on responses of thermoelastic interactions in a generalized thermoelasticity with memory-dependent derivatives inside a thick plate

The present work is carried out under generalized thermoelasticity theory with memory-dependent derivatives. The main purpose of this work is to analyze the thermoelastic interactions inside an infinitely extended thick plate due to axis-symmetric temperature distribution applied at the lower and upper surfaces of the plate under memory-dependent generalized thermoelasticity. The formulation of the problem is done in the context of the theory of thermoelasticity under memory-dependent derivatives with inclusion of time delay parameter [Formula: see text] and kernel functions that are defined in a slipping interval [Formula: see text]. The potential function concept along with Laplace and Hankel transform techniques is used to solve the problem. Furthermore, inversion of the Hankel transform technique is used to find the solution in the Laplace transform domain. The final solution in the space–time domain is obtained by employing a numerical method of Laplace inversion. We have also compared the present findings with work which has been done earlier. An analysis and the comparison of all the physical fields inherent to the generalized thermoelasticity with one relaxation parameter are given in a detailed way. The special findings and differences of using different kernel functions are highlighted.

Assessment of the Advantages of Static Shoulder FSW for Joining Aluminium Aerospace Alloys

Stationary (or Static) Shoulder Friction Stir Welding (SS-FSW) is a variant of FSW that was developed primarily to improve the weldability of titanium alloys by reducing the through thickness temperature gradient. Surprisingly, SS-FSW has been largely ignored by the Al welding community because it is widely supposed a rotating shoulder is an essential aspect of the process and that the higher conductivity means the surface heating effect of the shoulder is generally beneficial. In the work presented it is shown that SS-FSW has major advantages when welding high strength aluminium alloys; including a reduction in the heat input, a massive improvement in surface quality, and a narrower and more symmetric temperature distribution, which leads to narrower welds with a reduced heat affected zone width and lower distortion. The reasons for these benefits are discussed based on a systematic study aimed at directly comparing both processes.

Thermoelastic Characteristics in Thermal Barrier Coatings with a Graded Layer between the Top and Bond Coats

A graded layer was introduced at the interface between the top and bond coats to reduce the risk of failure in a thermal barrier coating (TBC) system, and the thermoelastic behavior was investigated through mathematical approaches. Two types of TBC model with and without the graded layer, subject to a symmetric temperature distribution in the longitudinal direction, were taken into consideration to evaluate thermoelastic behaviors such as temperature distribution, displacement, and thermal stress. Thermoelastic theory was applied to derive two governing partial differential equations, and a finite volume method was developed to obtain approximations because of the complexity. The TBC with the graded layer shows improved durability in thermoelastic characteristics through mathematical approaches, in agreement with the experimental results. The results will be useful in discovering technologies for enhancing the thermomechanical properties of TBCs.