Simulate to prepare for a rainy day
The vast increases in computing capacity in recent times have enabled modelling techniques to be used in the study of divergent and complex phenomena. Modelling can be used to study a myriad of scenarios in process events and their consequences. The information can be used to minimise harmful effects and to evaluate what actions are required if a dangerous situation should arise.
With the help of Computational Fluid Dynamics (CFD), we can predict risks and ensure that we are better prepared for dangerous situations. It can, for example, be used to simulate the spread of hazardous chemicals in a facility or building, or into the environment. In the case of a leak into the environment, it is necessary to be familiar with evacuation requirements in order to protect humans from exposure to harmful chemicals. In the event of a fire, smoke and soot significantly affect visibility, which necessitates the evaluation of worst-case scenarios in advance.
So what can we model with CFD?
What if there is a fire or explosion inside a building or hazardous materials leak? If a fire breaks out indoors the spread of smoke can be modelled and resultant visibility problems identified. A working evacuation plan can be drawn up based on this information.
Different kinds of explosions and subsequent shock waves, heat, and radiation levels can also be modelled. Knowing what chemical is used in a process, for instance, is enough to evaluate the effect of an explosion on surrounding buildings. This information can be used to dimension structures to be sufficiently durable or to reduce pressure waves as much as possible.
When hazardous emissions occur indoors it is essential to contain it is as quickly as possible. If the location of an emission source is known, modelling can reveal how ventilation can prevent dangerous situations from occurring or how the emission can be contained within the building.
The severity of the harmful effects of a leak or spill on the environment is dependent on the landscape, wind and, in some cases, humidity. These factors can all be taken into account in a CFD model. Once the geometry of a production facility and its surroundings is known, different situations incorporating, for example, changing wind speeds and directions can be modelled. This information can be used to locate buildings optimally to prevent pollution or reduce its harmful effects. If there are several potentially hazardous sources they can be studied individually or in combination for a worst-case scenario situation.
How then can health, costs and operational reliability be taken into account?
With the help of modelling, threshold values can be calculated for the authorities. Almost all chemicals and particles have known threshold limits that allow the evaluation of health and other effects on persons exposed to such materials. It is crucial to have accurate information about the concentration of particles and chemicals so that clearance distances and other preventative measures can be taken.
The time of exposure is sometimes also significant in the amount of damage caused. It is, therefore, important to be able to evaluate the duration of different events. Some alarm systems measure both concentration levels and the time of exposure. The alarms are triggered when threshold limits are exceeded, leading to production downtime. It is, therefore, important when designing a production facility that potentially dangerous situations are studied and, based on the information gathered, to locate production lines and storage tanks so that domino effects that can be of even greater danger are prevented. The information should be used to design alarm systems so that they function safely, but also to avoid unnecessary alarms that cause production downtime. An unnecessary alarm can, for instance, be triggered due to sensors that are badly located.
With modelling we can predict risks and plan accordingly to save human lives, increase well-being at work and boost productivity should an accident occur. We cannot mitigate all risk, but thorough preparation with the help of an expert can go a long way to ensuring long-term cost savings and the safety of human lives, property and the environment.
Author: Heidi Niskanen