Search

This paper presents and discusses the results of the transient numerical simulation carried out for an isolated main rotor model and a helicopter in vertical descent autorotation by developing the 6-degree of freedom, rigid-body equations of helicopter motion. The Unsteady Reynolds Averaged Navier-Stokes model is used to simulate the unsteady flow field surrounding four-bladed BO-105 isolated main rotor and complete helicopter which includes the fuselage and the tail rotor. The principal autorotation characteristics for the helicopter such as induced velocity, rate of descent, main rotor angular speed, thrust and torque have been calculated. The simulation results show the creation of a spanwise flow on the upper surface of the blade, and moving fluid in the direction of the blade tip in a region downstream and beneath the leading edge vortex. The aerodynamic characteristics on the complete helicopter are similar to the ones attained for the isolated rotor simulation. [ABSTRACT FROM AUTHOR]

Light pipes transmit daylight into building interiors. Their installation into thermally insulated roofs of low energy buildings can be a problem because of thermal bridges and condensation problems. This article is focused on a CFD simulation thermal analysis that includes four variations of light pipes with a segment of a flat roof. Common light pipes with a hollow light guiding tube were compared to special light pipes containing an additional glass unit located inside the tube. The additional glass units increase thermal resistance and reduce condensation risks of the light guiding systems. The light pipes were compared in two different simulation models run in ANSYS Fluent software and the CalA program. Temperature profiles and air flow patterns of the cross sectional profiles of the light pipes served to determine the total heat transmittance and heat losses of the studied light pipes installed in a segment of a thermally insulated flat roof. The paper compares simplified 2D rotational–symmetrical numerical model based on the thermal diffusion equation with the complex 3D CFD numerical simulation. The results confirm that the simplified 2D numerical model is suitable for the thermal evaluation of the light pipes containing an additional glass unit, too. The additional glass unit with the triple glass improves thermal resistance up to 88% in case of light pipe with diameter 600 mm and reduces optical transmittance to 28%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Analyses are conducted focused on climate adaptive reactions of BiPV facade system. • System's performance prediction is relevant for energy-efficient buildings. • Optimisation techniques yielded an increase in total thermal and energy performance. Ventilated building-integrated photovoltaic (BiPV)/phase-change material (PCM) façades have been applied and validated in building energy simulations; however, the dynamic thermal response of these façades has not been investigated. Notably, performance predictions and simulations for systems featuring natural airflows in the façade cavity are important for guiding the decision-making for energy-efficient buildings. To address this challenge in literature, in this work, numerical analyses were conducted, focusing on the climate adaptive reactions of a BiPV façade system coupled with a latent thermal energy storage system, based on a PCM. Numerical methods for determining the PCM heat transfer were evaluated, including their limitations. The thermodynamic reactions of two BiPV façade concepts were comparatively studied using two simulation domains: building energy simulations and computational fluid dynamics. The reliability of the theoretical methods was also evaluated. Good agreement between the simulation results and experimental data was noted through dynamic outdoor tests, empirically validating the study; standard statistical indicators were calculated and employed to assess the consistency between the experimental and simulation results. The used numerical approach can reliably predict the thermo-responsive capabilities of PCM-based BiPV façades with respect to the overall tendencies. The parameter variation techniques revealed modifications in the overall thermal and energy performance of the façade system. The most undesirable instance of overheating was predicted when using RT27; therefore, the PCM is considered inappropriate in this case. [ABSTRACT FROM AUTHOR]