Christoph van Treeck

Dimensional reduction of 3D building models using graph theory and its application in building energy simulation

Since the various people involved in the design process for a building project tend to hold conflicting views, this inevitably leads to a range of disparate models for planning and calculation purposes. In order to interpret the relevant geometrical, topological and semantical data for any given building model, we identify a structural component graph, a graph of room faces, a room graph and a relational object graph as aids and explain algorithms to derive these relations. We start with a building model by transferring its geometrical, topological and semantical data into a volume model, decomposing the latter into a so-called connection model and then extracting all air volume bodies and hulls of the model by means of further decomposition into elementary cyclic connection components. The technique is demonstrated within the scope of building energy simulation by deriving both a dimensionally reduced object model required for setting up a thermal multizone model and a geometrical model for defining single or multiple computational fluid dynamic domains in a building together with incidence matrices correlating these models. The algorithm is basically applicable to any building energy simulation tool.

Computational steering on distributed systems: Indoor comfort simulations as a case study of interactive CFD on supercomputers

This paper presents the current state of a computational steering system for interactive computational fluid dynamics (CFD) simulations, allowing engineers to simulate interactively indoor climate and to evaluate human comfort. The tools presented support cooperative planning and design by providing means for interactively adding, removing and modifying geometry and boundary conditions online during a CFD simulation. To ensure interactivity and short-latency updates even for high-resolution runs the parallel Lattice–Boltzmann-based simulation kernel is optimized for high-performance computing systems. Emphasis is placed on the computational steering architecture, connecting a supercomputer with one or more visualization workstations. In particular, we show how a high-performance communication between simulation and visualization or steering front-end can be achieved together with preserving a flexible mechanism of on-the-fly attachment of multiple cooperation clients.

Integrated thermal comfort analysis using a parametric manikin model for interactive real-time simulation

Following the work of Fiala (Fiala, D., Lomas, K., and Stohrer, M., 2001. Computer prediction of human thermoregulatory and temperature-responses to a wide range of environmental conditions. International Journal of Biometeorology, 45, 143–159) we developed and tested a parametric multi-segment manikin model as the interface between Fialas human thermoregulation model and other computational codes for studying transient and local effects of thermal sensation and comfort perception. The model allows for motion control by transforming body parts according to an armature model which relates topological dependencies. The position of joints and decomposition into segments is chosen in terms of the settings of Fialas model. Several faceted geometric models are available such as the NASA MSIS Standard or predefined NASTRAN geometries. The developed thermoregulation interface provides means to computational steering, i.e. to interact with an ongoing simulation. The boundary conditions, the type of clothing, or the activity level can be modified online, results are updated on a real time scale during the simulation. The visualization on the artificial skin of the manikin includes the surface/skin temperatures and the local thermal sensation votes (LTSV); likewise the predicted mean vote (PMV) and the dynamic thermal sensation (DTS) are output. The LTSV data are based on experimental data which were obtained in a test chamber involving 24 test subjects for three levels of clothing insulation and a light level of activity.

Engineering-Based Thermal CFD Simulations on Massive Parallel Systems

The development of parallel Computational Fluid Dynamics (CFD) codes is a challenging task that entails efficient parallelization concepts and strategies in order to achieve good scalability values when running those codes on modern supercomputers with several thousands to millions of cores. In this paper, we present a hierarchical data structure for massive parallel computations that supports the coupling of a Navier–Stokes-based fluid flow code with the Boussinesq approximation in order to address complex thermal scenarios for energy-related assessments. The newly designed data structure is specifically designed with the idea of interactive data exploration and visualization during runtime of the simulation code; a major shortcoming of traditional high-performance computing (HPC) simulation codes. We further show and discuss speed-up values obtained on one of Germany’s top-ranked supercomputers with up to 140,000 processes and present simulation results for different engineering-based thermal problems.

Computational Steering of Complex Flow Simulations

Computational Steering, the combination of a simulation back-end with a visualisation front-end, offers great possibilities to exploit and optimise scenarios in engineering applications. Due to its interactivity, it requires fast grid generation, simulation, and visualisation and, therefore, mostly has to rely on coarse and inaccurate simulations typically performed on rather small interactive computing facilities and not on much more powerful high-performance computing architectures operated in batch-mode. This paper presents a steering environment that intends to bring these two worlds – the interactive and the classical HPC world – together in an integrated way. The environment consists of efficient fluid dynamics simulation codes and a steering and visualisation framework providing a user interface, communication methods for distributed steering, and parallel visualisation tools. The gap between steering and HPC is bridged by a hierarchical approach that performs fast interactive simulations for many scenario variants increasing the accuracy via hierarchical refinements in dependence of the time the user wants to wait. Finally, the user can trigger large simulations for selected setups on an HPC architecture exploiting the pre-computations already done on the interactive system.

In the Heat and Noise of the Moment : Effects on Risky Decision Making

Two studies, comprising 128 participants, were conducted to examine possible detrimental effects of noise and moderate heat stress on decision making. Three tasks involving risky decisions were used: a lottery choice task, the Balloon Analogue Risk Task, and two risk scenario questionnaires. Study 1 (n = 97) involved three noise stressors presented at 60dB(A) and a quiet condition. Compared with all other conditions, a radio podcast about the jubilee of museums caused a significant increase in risk aversion in the Choice Dilemma Questionnaire task. Study 2 (n = 31) compared two groups that completed the aforementioned tasks either in a warm (≥ 30°C) or neutral (≤ 25°C) ambient temperature condition. Participants made significantly riskier decisions in the warm ambient temperature condition in all tasks except the lottery task. Effects were more pronounced among female subjects. Especially elevated ambient temperatures should, therefore, be monitored in office environments to prevent impairments of decision making.

Integrale Planung BIM – Umsetzungserfahrungen im Projekt „Viega World“

Dieses Kapitel berichtet uber den Erfahrungsgewinn bei der Umsetzung der „Integralen Planung BIM“ beim Neubau des Seminarcenters „Viega World“ in Attendorn als Referenzprojekt fur die Anwendung von BIM in der Gebaudetechnik.

BIM for Energy Analysis

This chapter addresses BIM in the context of energy demand calculation and building performance simulation. The focus is on different methods to identify the energy demand as well as on building services engineering, including references to the respective standards and calculation bases. We will present data exchange formats that can be used to exchange and to model the energy-related specifications of buildings and its systems and installations – and we will discuss the necessary requirements and definitions regarding the aspects of geometry, zoning, as well as semantics. The chapter also briefly discusses the current state of software-support for HVAC engineering calculations and dimensioning. Furthermore, we focus on the process chain for the use of BIM in the scope of energy demand calculation and simulation, including a brief discussion of the corresponding Model View Definitions of the Industry Foundation Classes. The chapter closes with an outlook on current research and development projects.

Too hot to carry on? Disinclination to persist at a task in a warm office environment

Abstract We investigated the effect of an elevated ambient temperature on performance in a persistence task. The task involved the coding of incorrect symbols and participants were free to decide how long to spend performing this task. Applying a between-subject design, we tested 125 students in an office-like environment in one of the three temperature conditions. The comfort condition (Predicted Mean Vote [PMV] = 0.01) featured an average air temperature of 24 °C. The elevated ambient temperature condition was 28 °C (PMV = 1.17). Condition three employed an airstream of approximately 0.8 m/s, intended to compensate for performance decrements at the elevated air temperature (28 °C, PMV = 0.13), according to Fanger’s thermal comfort equation. Participants in the warm condition were significantly less persistent compared with participants in the control and compensation conditions. As predicted by the thermal comfort equation, the airstream seemed to compensate for the higher temperature. Participants’ persistence in the compensation and comfort conditions did not differ. Practitioner Summary: A laboratory experiment involving a simulated office environment and three ambient temperature conditions (24 °C, 28 °C and 28 °C plus airstream) showed that persistence at a task is significantly impaired at 28 °C. An airstream of 0.8 m/s at 28 °C compensated for the disinclination to persist with the task.

Uniform segment-wise body parametric convection heat transfer coefficient model for sitting posture in vehicles

In many industrial multi-physics engineering applications, models need to capture the heat transfer effects of spatial and temporal changes in conditions around the human body. For thermal comfort assessment, convection heat transfer coefficients (hc) form part of the heat balance equation of the human body. In many non-uniform flow conditions, due to the turbulently mixed or stratified environment, convection heat transfer varies significantly on the human body. Parametric, segment-wise applicable convection heat transfer correlations are seen as an alternative in order to bridge these scales and levels in space and time. Therefore, robust reduced-order convective heat transfer models are needed for predicting heat transfer between the human body and its surroundings. The main goal of this research is to develop a reduced order model database that provides the segment-wise convective heat transfer coefficients (hc) for typical indoor flow responses in multiple applications. In this article, a new parametric approach was detailed for estimating segment-wise body convection heat transfer coefficients for sitting posture in vehicles. The methodology follows a new strategy, i.e., in this application domain, here a car cabin, primarily relevant parameters are identified which affect the convective heat exchange. Following the sensitivity analysis of numerous computational fluid dynamics simulations with varying conditions, we identify relevant primary variables and heat transfer coefficients correlations and test the model robustness accordingly. A database-driven approach is developed in order to make correlations accessible during simulations, for example addressing energy performance. Finally, the experimentally investigated heat transfer analysis around the human body is presented and later compared with numerically reproduced data.