Abstract: Two different approaches are undertaken to investigate the interaction of planar shock waves with circular cylinders. Experiments are conducted in a shock-tube apparatus equipped with a schlieren-based optical system to monitor the interaction, and numerical simulations are carried out using an in-house computer code to simulate similar problems. The incident shock-wave Mach number is varied in the range 1.1–1.4. Excellent agreement is found between the simulations and the experiments in terms of shock patterns, even though the model is based on an inviscid approach. Quantitative comparisons between the experimental results for different initial conditions (shock-wave strength, cylinder diameter, and working gas) are made to find the physical parameters affecting the path of the reflected shock. An approximate universal relation is derived, which predicts the reflected-shock trajectory along the axis of symmetry as a function of the incident-shock Mach, the diameter of the cylinder, and the gas properties. This relation is valid in the vicinity of the cylinder in the range of 0.1–5 D, where D is the cylinder diameter. It is found that the reflected shock from the cylinder evolves as in the case of a reflected-shock wave from a planar wall multiplied by a reduction factor, which depends on the incident-shock Mach number and the ratio of specific heats.
Permalink: https://doi.org/10.1103/physreve.83.066317

Abstract: This paper reports high resolution simulations using fifth-order weighted essentially non-oscillatory (WENO) schemes with a third-order TVD Runge-Kutta method to examine the features of turbulent mixing layers. The implementation of high-order WENO schemes for multi-species non-reacting Navier-Stokes (NS) solver has been validated through selective test problems. A comparative study of performance behavior of different WENO schemes has been made on a 2D spatially-evolving mixing layer interacting with oblique shock. The Bandwidth-optimized WENO scheme with total variation relative limiters is found to be less dissipative than the classical WENO scheme, but prone to exhibit some dispersion errors in relatively coarse meshes. Based on its accuracy and minimum dissipation error, the choice of this scheme has been made for the DNS studies of temporally-evolving mixing layers. The results are found in excellent agreement with the previous experimental and DNS data. The effect of density ratio is further investigated, reflecting earlier findings of the mixing growth-rate reduction.
Permalink: https://doi.org/10.1007/s10915-010-9429-3

Abstract: This paper describes the implementation of immersed boundary method using the direct-forcing concept to investigate complex shock–obstacle interactions. An interpolation algorithm is developed for more stable boundary conditions with easier implementation procedure. The values of the fluid variables at the embedded ghost-cells are obtained using a local quadratic scheme which involves the neighboring fluid nodes. Detailed discussions of the method are presented on the interpolation of flow variables, direct-forcing of ghost cells, resolution of immersed-boundary points and internal treatment. The method is then applied to a high-order WENO scheme to simulate the complex fluid–solid interactions. The developed solver is first validated against the theoretical solutions of supersonic flow past triangular prism and circular cylinder. Simulated results for test cases with moving shocks are further compared with the previous experimental results of literature in terms of triple-point trajectory and vortex evolution. Excellent agreement is obtained showing the accuracy and the capability of the proposed method for solving complex strong-shock/obstacle interactions for both stationary and moving shock waves.
Permalink: https://doi.org/10.1016/j.jcp.2010.11.016

Abstract: [Norwegian] Anvisningen viser bruken av energiberegningsprogrammet TEK-sjekk Energi. TEK-sjekk Energi kan gjøre kontrollberegninger mot kravene gitt i TEK10 § 14, NS 3700 eller NVE sin energimerkeordning for bygninger. Alle bygningskategoriene i TEK10 og i energimerkeordningen kan beregnes. Bruksanvisningen er et supplement til hjelpen som ligger i TEK-sjekk Energi i form av kommentarer til mange av cellene i regnearket.

Abstract: Demand controlled ventilation (DCV) can considerably reduce the ventilation airflow rate and energy use for fans, heating and cooling compared to constant air volume (CAV) ventilation. Based on the new EPBD Recast directive from the EU Parliament, there is a potentially enormous upcoming marked for converting from CAV to efficient DCV in existing commercial buildings. However, several DCV-solutions are not very suitable for upgrading applications because they require redesign of airflow paths or introduction of several new components that are difficult to integrate into existing CAV-systems. A normal consequence is that ventilation upgrading is postponed, or the existing ventilation system is completely discarded and replaced. Such complete replacement of existing systems is probably not environmentally friendly, and has considerable additional costs like loss of estate rental income during the rebuilding period. This paper presents DCV-systems that seem particularly promising for upgrading ventilation in existing commercial buildings. At the moment, DCV with variable supply air diffusers seems generally most suitable for upgrading from CAV to VAV, but project-specific requirements and circumstances must be emphasized before the final choice in each project is taken.

Abstract: Keywords: Demand controlled ventilation, Energy performance, Building controls & automation, Ventilation, Schools

Abstract: This article explores the critical role of Demand Controlled Ventilation (DCV) systems in achieving substantial energy savings within the building sector, especially in light of the urgent need to reduce manmade CO₂ emissions as recommended by the IPCC and the European Union’s directive for nearly zero energy buildings (NZEB) by 2020. Through an in-depth analysis of different DCV systems, including Pressure Controlled DCV, Static Pressure Reset DCV, and Variable Supply Air Diffuser DCV, the paper highlights the energy-related differences and potential improvements for these systems. It critically evaluates the performance of traditional and modern DCV systems in non-residential buildings, revealing the often unmet potential for energy savings due to various factors, such as inadequate specifications, poor system reliability, and lack of comprehensive responsibility in system implementation. By presenting new requirements for well-functioning DCV systems based on identified success criteria, the article proposes a framework for enhanced energy functionality. This includes recommendations for specific fan power (SFP) control, clear definition of system functionality responsibility, and the importance of accurate component specification and system review post-implementation. The findings underscore the necessity for more reliable DCV systems to close the gap between theoretical and actual energy performance, thereby contributing significantly to the sector’s ambitious energy goals.

Abstract: To indentify indoor air quality in one office and one kindergarten with and without local electrostatic air cleaners or local HEPA air Cleaners. Keywords: Field studies, Particles, Air cleaning, Irritation

Abstract: Keywords: Schools, Human subjects, Irritation