Related Experiment Video
Updated: Jul 1, 2026
08:16
Combustion Characterization and Model Fuel Development for Micro-tubular Flame-assisted Fuel Cells
Published on: October 2, 2016
Comparison of emission models with computational fluid dynamic simulation and a proposed improved model
James S Bennett1, Charles E Feigley, Jamil Khan
1Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Division of Applied Research and Technology, Engineering and Physical Hazards Branch, 4676 Columbia Parkway MS-R5, Cincinnati, OH 45226, USA.
Summary
Comparing airborne contaminant models, the uniform diffusivity (UD) model showed the lowest error for steady-state emissions. For time-varying sources, a location-specific model (CM-L) provided the most accurate emission estimates.
Area of Science:
- Environmental Engineering
- Occupational Health and Safety
- Computational Fluid Dynamics
Background:
- Accurate estimation of airborne contaminant sources is crucial for controlling workplace exposure.
- Industrial hygienists often infer emission data from room concentration measurements, a complex task.
- Existing models simplify contaminant transport, but the resulting errors are not well understood.
Purpose of the Study:
- To compare the accuracy of different emission estimation models against computational fluid dynamics (CFD) simulations.
- To evaluate the impact of source and receptor locations on model performance.
- To develop and assess an improved time-dependent emission model.
Main Methods:
- Employed CFD simulations (Fluent 4) to generate workplace airflow and concentration fields.
- Compared single-zone completely mixed (CM-1), two-zone completely mixed (CM-2), and uniform diffusivity (UD) models.
- Conducted numerical experiments with factorial combinations of source/receptor locations, airflow rates, and generation profiles (constant/time-varying).
Main Results:
- For steady-state conditions, the UD model demonstrated the lowest error compared to CFD.
- Model performance varied with source and receptor proximity; CM-2 was better when the receptor was in the source near-field.
- A location-specific mixing factor improved accuracy, with the developed CM-L model outperforming CM-1 and CM-2 for time-varying sources.
Conclusions:
- The uniform diffusivity (UD) model offers better accuracy for steady-state emission estimation than CM-1 and CM-2.
- Source and receptor location significantly impact emission estimates, particularly for the CM-1 model.
- The developed CM-L model, incorporating location-specific factors, provides a more accurate approach for time-dependent emission modeling.
Related Concept Videos
01:07Laminar and Turbulent Flow
Fluid dynamics is the study of fluids in motion. Velocity vectors are often used to illustrate fluid motion in applications like meteorology. For example, wind—the fluid motion of air in the atmosphere—can be represented by vectors indicating the speed and direction of the wind at any given point on a map. Another method for representing fluid motion is a streamline. A streamline represents the path of a small volume of fluid as it flows. When the flow pattern changes with time, the streamlines...
01:17Accelerating Fluids
When a fluid is in constant acceleration, the pressure and buoyant force equations are modified. Suppose a beaker is placed in an elevator accelerating upward with a constant acceleration, a. In the beaker, assume there is a thin cylinder of height h with an infinitesimal cross-sectional area, ΔS.
The motion of the liquid within this infinitesimal cylinder is considered to obtain the pressure difference. Three vertical forces act on this liquid:
The motion of the liquid within this infinitesimal cylinder is considered to obtain the pressure difference. Three vertical forces act on this liquid:
01:24The Kinetic Model of Gases
The kinetic model of gases explains the properties of a perfect gas using three main assumptions: molecules move in ceaseless random motion, their size is negligible compared to the distances between them, and they do not interact except during perfectly elastic collisions. The total energy of a gas is the sum of the kinetic energies of all its constituent molecules. The pressure exerted by the gas arises from the continual bombardment of the container walls by billions of colliding molecules.
01:12Modeling and Similitude
Scaled modeling is a fundamental technique in engineering, enabling the study of large and complex systems by creating smaller, manageable replicas that recreate critical characteristics of the original. In hydrology and civil infrastructure, for example, scaled models of dams help analyze water flow, turbulence, and pressure. This method allows for accurate predictions of real-world behavior within a controlled environment, significantly reducing the cost and time involved in full-scale...
01:30Typical Model Studies
Fluid mechanics model studies often utilize scaled-down systems to predict fluid behavior in full-scale environments, such as river flows, dam spillways, and structures interacting with open surfaces. Maintaining Froude number similarity in river models is crucial, as it replicates surface flow features like wave patterns and velocities.
01:21Design Example: Creating a Hydraulic Model of a Dam Spillway
Scaled hydraulic models of dam spillways provide a practical way to replicate and study the intricate flow dynamics of these structures. Often built to a 1:15 ratio, these models allow for observing critical water behavior, such as velocity distribution, flow patterns, and energy dissipation.