Room Geometry Research Articles

Influence of room geometry and ventilation rate on airflow and aerosol dispersion : implication for worker protection. Whicker, J. J., Wasiolek, P. T., and Tavani, R. A. : Health Phys., 82(1): 52-63, 2002.(Abstracts of foreign literature)

Influence of room geometry and ventilation rate on airflow and aerosol dispersion : implication for worker protection. Whicker, J. J., Wasiolek, P. T., and Tavani, R. A. : Health Phys., 82(1): 52-63, 2002.(Abstracts of foreign literature)

Validation–comparison of predicted and measured levels in industrial spaces

Financed by the German Federal Agency for Labor and Social Affairs, several methods of calculating the noise propagation in industrial halls were used for about 150 halls and compared with measurements. With all noise sources, such as machines and equipment stopped, a dodecahedron loudspeaker emitting broadband noise was used, and the octave-band levels were measured on different propagation paths. The room geometry and equipment in the room were entered into uniform datasets, the calculation methods were applied to each dataset, and the results in terms of deviations between calculated and measured values were evaluated statistically. The prediction method with the smallest deviations was chosen for further evaluation. This method, which uses mirror images with approximations and takes into account diffraction with a method first developed by Kuttruff and extended by Jovicic, uses mean values for fittings and absorption at walls and ceilings. This method has been incorporated into VDI 3760, and will be extended in the future to take into account screening by single objects and the real distribution of absorptive materials on surfaces. Representative experimental results, calculation techniques, predicted levels, and deviations between measured and predicted levels are presented.

Generation of variational standard plant room solutions

We have used the object-based CAD programming to take advantage of standardisation to handle the selection, sizing, layout and (potentially) pipe routing for Low-Pressure Hot Water (LPHW) plant rooms in buildings. Our approach combines automation and interactivity. From a simple specification of the plant room geometry (an orthogonal polygon with known obstructions, openings and external walls), and the heating load in kW, our software proceeds through a number of steps. First, the number and size of standard modular boilers, pumps, etc., are determined from the heat load. Then, a compatible optimising 3D variational solution is generated, using Constraint Logic Programming. To do this, we firstly enumerate a satisfactory topological solution, and then refine it to form a compatible geometrical solution. The final step generates pipe routes, using optimisation techniques to minimise the length of pipes and the number of bends. The solution obtained can be modified or improved by the designer, for which we have interactivity. Modifying the topology of the solution or the geometry of the plant room is done directly through the graphic interface, e.g. modifying a boiler position is done by dragging; the system automatically updates the 3D model including the pipe routing while maintaining all the design rules. The solutions generated by our prototype have been tested against conventional solutions in a benchmarking exercise. Advantages have been underlined and suggestions for further development have been made.

Low‐frequency assessment of the in situ acoustic absorption of materials in rooms: an inverse problem approach using evolutionary optimization

AbstractThe in situ assessment of the acoustic absorption of materials is often a necessity. The need to cover the whole frequency range of interest for the building engineer has led the authors to an approach involving two frequency‐complementary measurement methods. This paper deals with the part dedicated to low frequencies. The measurement is defined here as a boundary inverse interior problem. A numerical model of the room under investigation, allowing for the computation of the pressure field in the volume, given impedance boundary conditions and a point source, is combined to a global optimization algorithm. The algorithm explores the set of possible boundary conditions in order to minimize the difference between the computed pressure values and the one observed at a few measurement points, leading to the determination of all the boundary conditions at a time. In practice, the finite element method (FEM) or the finite difference method (FDM) is used here to model the room and an Evolution Strategy as the optimization tool. After describing the ES operators, a numerical study is carried out on simulated measurements, both on problem‐ and algorithm‐specific parameters, in the case of an academic two‐dimensional room geometry. The method is then applied to a three‐dimensional room with promising results. Copyright © 2002 John Wiley & Sons, Ltd.

PREDICTING NEAR–FLOOR AIR VELOCITIES FOR A SLOT–INLET VENTILATED BUILDING BY JET VELOCITY DECAY PRINCIPLES

Air velocities near the floor of slotventilated buildings are the result of interaction between the supply air jet andthe geometry of the confined space. To predict air velocity, the effect of the inlet air jet momentum and the room geometryhas to be included.<br><br>Air movements in a 5 m wide 3 m high 8.5 m deep empty slotventilated room were studied for two different jetmomentum situations under isothermal conditions. A negativepressure ventilation system supplied air through a slot wallinlet with an adjustable flap. The inlet was installed beneath the ceiling. The exhaust air was taken out through a section ofslatted floor along the inlet wall. Air velocity distribution in the room was recorded with a multichannel measurement system.To study the center velocity decay of the incoming jet and the return airflow, the data used in this report are concentrated onthe measurement points near the ceiling and the floor.<br><br>The experiment showed that a given nearfloor air velocity may be generated by choosing a proper supply jet momentum.Threedimensional effects occurred in the symmetrical, empty room. Mean velocity prediction in the nearfloor region wasanalyzed on the basis of supply jet momentum and room geometry. The prediction was accurate for the maximum nearfloorair velocity that occurred near the end wall opposite the inlet. As the air returned along the floor towards the inlet wall, themeasured velocity became consistently lower than the predicted value.

Influence of room geometry and ventilation rate on airflow and aerosol dispersion: implications for worker protection.

Knowledge of dispersion rates and patterns of radioactive aerosols and gases through workrooms is critical for understanding human exposure and for developing strategies for worker protection. The dispersion within rooms can be influenced by complex interactions between numerous variables, but especially ventilation design and room furnishings. For this study, dependence of airflow and aerosol dispersion on workroom geometry (furnishings) and ventilation rate were studied in an experimental room that was designed to approximate a plutonium laboratory. Three different configurations of simulated gloveboxes and two ventilation rates (approximately 6 and 12 air exchanges per hour) were studied. A sonic anemometer was used to measure airflow parameters including all three components of air velocity vectors and turbulence intensity distributions at multiple locations and heights. Aerosol dispersion rates and patterns were measured by releasing aerosols multiple times from six different locations. Aerosol particle concentrations resolved in time and space were measured using 16 multiplexed laser particle counters. Comparisons were made of air velocities, turbulence, and aerosol transport across different ventilation rates and room configurations. A strong influence of ventilation rate on aerosol dispersion rates and air velocity was found, and changes in room geometry had significant effects on aerosol dispersion rates and patterns. These results are important with regards to constant evaluation of placement of air sampling equipment, benchmarking numerical models of room airflow, and design of ventilation and room layouts with consideration of worker safety.

The effect of wall angles near a speech source on hearing comfort

This study will involve a controlled experiment to determine the correlation between hearing comfort and lateral energy fraction (LEF). (Hearing comfort has also been described as ease of hearing, and is a measure of speech intelligibility.) LEF is dependent on the geometry of surfaces near the source. Therefore, in order to study the effect of the angle of reflective walls near a speech source on hearing comfort, rooms with identical reverberation time, noise level, and volume are modeled. The angle between walls near the speaker is the only physical variable. The RT in every room will be 0.6 s and the background noise will be exactly NC 25. The angle between reflective walls on either side of the speaker will be changed in 5° increments. The speaker is always located 3 ft. in front of the varying corner, and the listener is always located 15 ft. from source. This ensures that the signal to noise ratio can also be held constant. The data from this modeling experiment should explain the relationship between hearing comfort and room geometry, as measured by the lateral energy fraction.

Redistribution of the low frequency acoustic modes of a room: a finite element-based optimisation method

This paper presents a method to redistribute the acoustic modes of a room in the low frequency range. The relationship between the acoustic modes and the room geometry is studied. The fundamental problem of normalizing the acoustic modes of a simple, orthogonal room is examined in depth. Several variable local geometric modifications of the room walls are introduced and an optimisation procedure is developed, based on finite element analysis. This procedure is used for the calculation of the exact magnitude of the geometric modifications that will lead to smoother mode and consequently, smoother sound energy distribution in the frequency range of interest. The sound quality improvement of the modified room in the low frequency range with respect to ISO recommendations is verified. This work opens up the possibility of constructing acoustic laboratories with extended suitability to perform acoustic measurements in the low frequency range.

Radioactivity in building materials: room model analysis and experimental methods

First, models (room models) published in the international literature allowing the exposure to gamma radiation indoors due to building materials to be assessed are reviewed and discussed. For one of them, a sensitivity analysis concerning the effect of changing the parameters (e.g. dimensions of the room, thickness and density of the walls, etc.) used in calculations is performed. Second, a method is proposed for calculating the activity concentration in the walls of a room using: (a) the measured absorbed dose rate in air in the room; (b) the contributions of natural radionuclides ( 238U, 232Th and 40K) to the absorbed dose rate in air assessed by means of gamma spectrometry indoors; and (c) the specific dose rate (nGy h −1 per Bq kg −1) of natural radionuclides, for the chosen room geometry, calculated with the room model.

Comparison of acoustical measurements, calculations, and software for a seminar room

The Verle Annis Gallery is a rectangular room with a volume of approximately 20&amp;lt;th&amp;gt;000 ft3. Used primarily for seminars, it is known for its poor acoustic qualities. Various acoustical parameters were measured in the space using MLSSA software. The results were compared to calculations based upon the room geometry and the acoustical properties of the room surfaces. Finally, CATT-Acoustic software was used to model the room in its present condition and also with the addition of acoustical treatment and sound reflecting panels. A novel mechanized device was designed to improve the sound isolation between two simultaneous presentations. A comparison of the measured, calculated, and simulated results are presented. [This work was partially supported by the Paul S. Veneklasen Research Foundation.]

Subjective threshold of sound strength (G) due to level changes in the early sound field: Preliminary results

Acoustical measurements and related subjective studies over the past two decades have shown that increased early reflections produce increased sound strength, G in concert auditoria. The temporal distribution of early reflected sound and the role of room geometry have been found to be important design related factors relating to both G and acoustical intimacy, and therefore to hall quality in general [J. R. Hyde, Proc. 16th ICA, Seattle, Paper 1aAA3 (1998)]. A listening test was devised to determine the threshold of perception of changes in loudness relative to changes in the level of the early sound field. The test setup consisted of direct and single-delay speaker channels in a semi-anechoic room, using brief samples of different styles of symphonic music. Subjects were asked to choose the louder of two paired samples of the same musical passage, played in rapid succession. Preliminary results from ‘‘unsophisticated’’ test subjects indicate that the perception threshold of loudness difference occurs when the total sound strength G varies by 1.0 dB due to the addition of a single early reflection at about −6 dB. Details and results of the experiment will be presented, and ideas for future work and test procedures will be solicited.

Updating egocentric representations in human navigation

Seven experiments tested whether human navigation depends on enduring representations, or on momentary egocentric representations that are updated as one moves. Human subjects pointed to unseen targets, either while remaining oriented or after they had been disoriented by self-rotation. Disorientation reduced not only the absolute accuracy of pointing to all objects (‘heading error’) but also the relative accuracy of pointing to different objects (‘configuration error’). A single light providing a directional cue reduced both heading and configuration errors if it was present throughout the experiment. If the light was present during learning and test but absent during the disorientation procedure, however, subjects showed low heading errors (indicating that they reoriented by the light) but high configuration errors (indicating that they failed to retrieve an accurate cognitive map of their surroundings). These findings provide evidence that object locations are represented egocentrically. Nevertheless, disorientation had little effect on the coherence of pointing to different room corners, suggesting both (a) that the disorientation effect on representations of object locations is not due to the experimental paradigm and (b) that room geometry is captured by an enduring representation. These findings cast doubt on the view that accurate navigation depends primarily on an enduring, observer-free cognitive map, for humans construct such a representation of extended surfaces but not of objects. Like insects, humans represent the egocentric distances and directions of objects and continuously update these representations as they move. The principal evolutionary advance in animal navigation may concern the number of unseen targets whose egocentric directions and distances can be represented and updated simultaneously, rather than a qualitative shift in navigation toward reliance on an allocentric map.

Test Room for Validation of Airflow Patterns estimated by Computational Fluid Dynamics

Symmetrical room geometry is not a sufficient condition for the design of a ventilated room where two-dimensional airflows are to be generated. Three-dimensional effects were observed in a symmetrically designed 3 m high by 5 m wide by 8·5 m long test room having a 0·019 m high slot inlet opening under the ceiling.The attached jet velocity profile measured at the ceiling in the symmetrical centre plane agreed well with the theoretical calculations based on two-dimensional flow, but large differences were found away from the symmetrical centre plane. The velocities in the jet 4·5 m downstream from the inlet wall were up to twice as high on one side compared to the other side. During the measurement period the side with high velocities occasionally changed without any obvious disturbance in the room. Smoke tests showed that the jet for some periods turned towards the right downstream corner, and then changed and turned to the left, thus showing a semi-stable flow behaviour. The measured velocities in the symmetrical centre plane were only slightly affected by the switch-over and remained at the same level throughout the experiment. In both semi-stable conditions, the return air direction diverged 30° from the symmetrical plane.Modification of the room with four 0·5 m high vertical guiding plates attached to the ceiling resulted in an acceptably uniform two-dimensional flow. The guiding plates changed the ceiling jet profile so it did not agree with the theoretical jet profile for an attached, two-dimensional flow. The maximum velocity became lower. At floor level, the direction of the return air was parallel to the symmetrical centre plane, without changes in the mean velocity.Systematic validation of flow behaviour is thus necessary before the assumption of two-dimensional flow could be accepted and a study is carried out in the symmetrical plane only.

Simplified method for risk oriented design of structural fire protection measures / Vereinfachte Methode zur risiko-orientierten brandschutztechnischen Auslegung von Bauteilen

On behalf of the German Federal Government a risk oriented simplified method for structural fire protection measures in nuclear power plants (NPP) based on a calculated fire load density qR has been developed. The burning behaviour of combustibles is described by the efficiency of combustion X. Depending on ventilation conditions, room geometry, fire load density and fuel distribution, the heating up of structural elements is calculated by means of a fire simulation zone model in multiple room configuration. The estimated temperature distribution within the structural element is compared with the temperature distribution gained by the fire conditions described by the standard temperature-time curve (ISO 834) and provides the equivalent time of fire exposure. The simplified design method needs only few empirical functions and design curves which are derived from systematic fire simulation calculations. The described method yields results which are in good correspondence with results from large-scale room fire tests and is comparable to other design methods, e.g. the method as applied in the German standard DIN 18230-1. In addition, heat sinks (e.g. large machines or reservoirs/vessels with fluids) can easily be considered by this methodology.

Links between concert hall geometry, objective parameters, and sound quality

For decades, the design of concert halls was driven by considerations of time history alone (T60, C80, ITDG), and as a result, little importance was attached to room geometry. The subjective importance of binaural dissimilarity has been a strong, though often simplistic, influence on recent designs. While listening experience has shown which fundamental room forms sound better than others, computer modeling and statistical analysis have enabled systematic investigation of the degree to which the geometry affects the sound. Using simple parametric models, this study will investigate effects of surface parallelism, concavity, and convexity on spatial and monaural objective acoustical parameters and on essential subjective attributes.

Using numerical simulation to predict ventilation efficiency in a model room

A computational fluid dynamics (CFD) code is used to simulate the air currents and the contaminant decay inside a small scale model room with forced ventilation through a simple supply and return. The numerical results are validated with flow visualization experiments and local clearance rate measurements by laser extinction. The comparisons show excellent agreement on the inlet side of the room and fair agreement on the outlet side. Based on the concept of local exponential tracer decay and mixing factor ( m), an arithmetic average of m is proposed as a measure of overall air ventilation efficiency η m. The proposed definition has practical benefit in numerical simulation because it reduces computational time without sacrificing the concept of air ventilation effectiveness. Examples of application are demonstrated by eviluating η m for different room configurations and ventilation arrangements. The calculated η m correlate well with the time required for evacuating the contaminants in different room configurations. The results show that, for the room geometry studied, a ventilation system performs better when the inlet and the outlet are perpendicular to each other than when they are parallel to each other, and that partitions in the room can have a significant influence on ventilation performance.

Males and females use different distal cues in a virtual environment navigation task

The study of navigational ability in humans is often limited by the restricted availability and inconvenience of using large novel environments. In the present study we use a computer-generated virtual environment to study sex differences in human spatial navigation. Adult male and female participants navigated through a virtual water maze where both landmarks and room geometry were available as distal cues. Manipulation of environmental characteristics revealed that females rely predominantly on landmark information, while males more readily use both landmark and geometric information. We discuss these results as a possible link between recent human research reporting hippocampal activation in spatial tasks and animal work showing sex differences in both spatial ability and hippocampal development.

Absolute localization for a mobile robot using place cells

This paper describes a method for absolute localization and environment recognition for an autonomous, sonar-equipped robot. The addition of an auto-associative memory to previously developed non-neural map making software results in a system that is capable of recognizing its environment and its position within the environment using remembered features and room geometry. In the prior system the robot used sonar to construct a metric map of an environment, but the map information had to be reconstructed each time the robot returned to an environment. We evaluated the system with a task that requires memory of the position of a goal that is not directly detectable by sonar.

Design considerations for Boettcher Hall, a vertical surround symphonic facility

In the early 1960s, Dr. Leo Beranek correlated reflection patterns in concert halls with qualitative listening experiences. Over the years, practitioners and other researchers have confirmed the validity of his work, proving that the direction, amplitude, frequency composition, and arrival time of the reflections define quality, regardless of room geometry. This paper discusses methods for achieving qualitatively preferred listening experiences in vertical surround halls such as Boettcher Concert Hall in Denver, Colorado, and the difficulties that can arise when breaking the mold of a traditional shoe-box hall.

Constitutive model of creep in rock salt applied to underground room closure

A multimechanism constitutive model of the creep of polycrystalline rock salt has been developed based on steady state creep as modified to incorporate transient creep through workhardening and recovery. Application of the model is in calculation of the closure of underground rooms excavated in a natural, bedded evaporite salt deposit. This requires an integrated technology consisting of not only the proper constitutive model, but also a range of other system elements relating to the site geology, initial and boundary conditions, and numerical methods peculiar to the application. Through finite element calculations, this model, with appropriate laboratory material parameters and a Tresca flow potential, has predicted the closure of a number of large, in situ experimental rooms at the Waste Isolation Pilot Plant (WIPP). In this paper, an overview of the model development, laboratory parameter generation and numerical simulation capability is given, together with a summary of the comparisons of the calculated and measured creep closure results. The comparisons encompass a range of test room configurations that exercise the predictive capability for stratigraphic setting, room geometry, thermal heating, stress field interaction and two and three-dimensional deformation fields. The simulations have proven satisfactory and suggest the general adequacy of the predictive technology.