Plume downwash stands for the downward migration of pollutants or smoke plumes directly to the lee (downwind side) of flow impediments such as buildings, bluffs, or smokestacks. It can adversely impact many people’s health and the environment. Therefore, a solid understanding of fluid dynamics is required for exhaust plumes descending from emission sources.

In this scenario, experts in computational fluid dynamics (CFD) analysis can step in to model the fluid flow, predict the behavior of a plume, and offer solutions. They are useful for anticipating how the plume will act in various scenarios and for developing plans to lessen its impact.

At present,  80% of environmental engineers rely on Computational Fluid Dynamics  (CFD) Analysis for their projects. The use of CFD to investigate plume downwash is one such critical application.

In this blog post, we explore the invisible mechanisms controlling downwash occurrences, captivating the interest of aeronautical science aficionados.

Plume Downwash: An Overview

When pollutants or smoke plumes travel downwards just behind obstructions, this motion is brought about by the obstacle’s generation of wake turbulence or lee cavity circulations. It brings higher-concentration pollutants down toward the ground. There are several life-threatening hazards associated with this phenomenon.

Hazards Associated with Plume Downwash

1. Increased Ground-Level Pollutant Concentrations: The entrainment of exhaust gasses released by short stacks or rooftop vents into the wakes of buildings can result in ground-level pollutant concentrations that are significantly larger than those from gasses released at the same height in the absence of the buildings.

2. Stack Location and Exhaust Gas Characteristics: The stack location and the characteristics of the exhaust gasses also play a role in the concentration of pollutants.

3. Air Pollution: When plumes come in contact with cold air, they drop pollutants used in cooling towers, namely, scale inhibitors, corrosion inhibitors, biocides, etc., and cause massive air pollution.

4. Spread of Diseases: Consequently, it can spread diseases such as legionnaires, and the people who live near cooling towers could be the subjects to various diseases.

5. Visual Impact: Plumes also have a visual impact as they cause fog formation, which can reduce visibility and cause transportation disruptions, especially in winter.

Plume Downwash: Role of a CFD Analysis Consultant

Here are the roles of a CFD Analysis Consultant in the study of plume downwash:

1. Understanding Fluid Flow: They use CFD tools and techniques to analyze and solve problems  related to fluid flow.

2. Analyzing Plume Behavior: This includes the behavior of exhaust plumes and their downward displacement, which is the essence of plume downwash.

3. Designing Cooling Towers: In the case of cooling towers, they can analyze, design, and optimize these structures to decrease the plume problem.

4. Conducting Plume Downwash Analysis: A computational model of the stack shell and liner(s) shall be constructed for the plume downwash study.

5. Analyzing Local Conditions: The plume downwash study shall include an analysis of the local wind/temperature data to identify the occurrence of critical wind and temperature conditions.

6. Maximizing Liquid Collection: The objective of the wet stack study shall be to maximize liquid collection downstream of the mist eliminators.

7. Preventing Ground Level Rainout: They work to preclude ground level rainout from the stack by recommending experimentally developed, tested, and optimized liquid collection devices and drainage systems to return collected liquid to the absorber with minimum re-entrainment.

8. Site Inspection & Supervision: They perform site inspection & supervision to verify and evaluate system performance before commissioning.

Mechartes: Leading CFD Analysis Consultant in Plume Downwash Hazard Mitigation and Solutions

At Mechartes, we are a leading CFD analysis consultant company with over 16 years of experience providing accurate simulation results with a professional approach and an engineering mindset. Our team of highly skilled engineers in Mechanical and Software Engineering offers precise simulations.

Plume Downwash Hazard Mitigation: Mechartes’ Goal

Our goal is to prevent ground-level rainout from the stack by recommending experimentally developed, tested, and optimized liquid collection devices and drainage systems.

Methodology

In the context of plume downwash, we use our expertise in being a CFD analysis consultant to analyze and solve problems related to fluid flow. This includes the behavior of exhaust plumes and their downward displacement.

Further, we perform the following:

• Designing and optimizing systems such as cooling towers to decrease the plume problem.

• Conducting a comprehensive plume downwash study, which includes constructing a computational model of the stack shell and liners, analyzing local wind/temperature data, and maximizing liquid collection downstream of the mist eliminators.

• Performing site inspection and supervision to verify and evaluate system performance prior to commissioning.

Our clients are delighted with the results we deliver, and our advanced methods, simulation algorithms, and computing power enable us to do so.

Exploring Plume with Mechartes: A Closer Look at Case Studies

Some of our remarkable roles as CFD Analysis Consultants in the case of plumes are:

1. Regulating Cooling Tower Plume in Winters

By delving into fluid dynamics and  optimizing the tower’s design, we used  CFD tools to generate a digital graphic illustrating plume dispersion. This predictive model allowed a comprehensive understanding of how the plume would disperse in the atmosphere.

2. CFD Analysis of the Cooling Tower

In a detailed analysis, we used CFD to optimize cooling tower performance and assess plume impact on nearby structures. We crafted a comprehensive 3D model of the cooling tower plant with CFD software.

A CFD wind tunnel featuring modeled nearby buildings facilitated the study of various parameters, including velocity, temperature, humidity, and the percentage of re-circulation at each inlet.

Discoveries revealed air recirculation ranging from 5 to 35%, resulting in an increased wet bulb temperature. Despite this, we observed no plume travel toward occupied areas, and the plume dissipated with ambient air.

Final Note

In the complex domain of plume downwash, Mechartes stands as a 16-year stalwart as CFD Analysis Consultants. Addressing hazards like heightened pollutant concentrations and air pollution, we not only analyze but actively mitigate risks.

With a focus on cooling tower optimization and comprehensive plume downwash studies, our commitment to precision is evident. Our advanced methodologies and adept use of CFD tools offer innovative solutions.

For those seeking expertise in hazard mitigation, visit our website to unlock a world where engineering meets excellence and plume downwash challenges are not just understood but effectively resolved.

Contact us today!