Monday, September 21, 2009

Computer Modeling Simulation

Although computer simulation in building is a main key for the study of energy efficiency in buildings first thing to consider is understand the definition of the computer simulation. Computer simulation is create a model of a theoretical physical system, complete this model on a digital computer program, analyze the output, compare the result and finally choose the best option which can give the most efficient result.

Inside the overall task of simulation there are three main sub-fields such as “model design, model execution and model analysis.” Simulation has a principle of leaning by practicing. To learn about the system is better to first build a model then operate this model. The use of simulation is an activity that is as natural as a child who role plays. Children understand the world around them by simulating. The majority of their connections with other people, animals, objects and their environment are based on learn by practice as well as make a mistake and gain experience. For instance they don’t know by pouring the sugar on the table they can build a sugar cone until they experience it. It is an opportunity that nature gave them to use their natural ability to learn during process. As an adult some of these childlike manners are lost during the time but it brings back to us through computer simulation design. In fact computer simulation is the electronic equivalent of role playing and it serves to drive synthetic environments and virtual worlds.

Simulation and modeling can be directly use as a design tool for any type of building and it has become essential part of many designs. It is a powerful and significant tool because offers a way to understand and explore different alternatives in design, plans and/or policies. Also it is less expensive, time-consuming and more practical to work with. Main advantage of simulation is before a building constructed it will allow the designers to optimize the energy use and efficiency of the building. During the design process designers have a chance to ask different question about the project like What if? Or how about this instead of that? These questions give them the opportunity to make changes as much as they want instead of changing the actual system.

In addition, for the exciting structures simulation could become a very helpful tool with the urge to improve efficiency of the buildings. Designers can model exciting building and try to optimize the energy use by varying different parameters in the structure such as window location, insulation materials, materials used for shading, lighting system, HVAC and air conditioning. Designers can monitor or measurer the impact of these changes on the overall energy efficiency and recommend changes to be implemented in the structure. With the recent development in the analysis and design tools modelers are able to correlate the simulation results with data collected from the actual structure. This has filled the gap between analyses and experiment.

Modeling process is a connection between designer, computer model, input data, and output result. Since many aspects of models need a fair conclusion designer and the model should be strongly connected to each other. As an example in the design process designer make an individual decision about which data is essential to use, how much detail need to be involved during the process and how to make the model more efficient and useful for public. In each particular project designer take time and effort to understand and recognize the limitation inherent in the model formulation, identify the errors, make a correction in details, calculation their response and obtain the best result.

Each model is generally designed for the specific project because in each project designer build the model based on the information and data on that specific situation and condition which is not similar to other circumstance. Sometimes the final result is not what a designer expected and it is fixable by comparison between simulation results. Also designer can check the result in different programs to get the most reasonable answer. After comparing the result in the simulation process designer need to replaced the exciting program to the better program if “better data is existing, more precise or more revealing analysis is performed on the data and an alternative formulation data provides as much insight with as much precision and more efficiently (lower data requirement or faster computational speed)”.

In the simulation programs the level of details of a model is a subject to concern. The model is worked based on variety detail and existing data which is really important in the modeling. Different programs give an opportunity to designers to add different type of detail during modeling but they should consider how much and what sort of detail they need to put in. Adding up the incorrect details to the process will change the numbers in the report and the result will not be practical at the end. The inclusion of extra detail can mislead the people because in some cases it shows that model is too expensive to use or need too much data requirement. Another duty of designer is collect all available data for the project because model can not create an outstanding result if data information does not exist or it is not completed. Also need to remember that if data were updated during the time of the design process it is a designer responsibility to replace or update the old information with new data.

Design process in meaning is similar to the meaning of investigation during design. If two designers attack a same challenge although they would naturally start from different points and process by dissimilar way they reach the same conclusion at the end. But during the design process both designers need to consider the all options such as R values, insulation, and door and window area and building construction.

Model should not be similar to a container that we just add information into it. The value of the model is dependent on the quality of the data, the way of designer using it and the amount of the details. It is good to remember that in design process first requirement for modelers is patient because sometimes the result of the work is disappointing and designers need to redo the all process of the design, add additional data to the program or compare data’s to get a better result. In general designers have three source of difficulty during their design process including:” experimental error (or noise), confusion of correlation with causation and complexity of the effects studies.”

If modelers consider some basic principles in modeling they make the design process simpler. “Model simple, think complicated” which means model doesn’t need to be as complicated as actuality and designers can think complex during process and have a simple final model. It seems little bit confusing because knowing how much simple or complicated the model needs to be is not an easy option to manage and some experience would be helpful. “Start small and add” is a second principle. The third principle is “dividing and conquers, avoid super large models”. As Pidd – professor of management science in the management school of Lancaster University- recommended in his paper, this is a common advice given to all modeler who is trying to understand how a complicated system operates. Designer should be stay away from falling in love with data and try to be realistic about them is another principle. The last principle for designers is “model building may feel like modeling through. “

Simulation system design in each project is developed by different alternative. In passive solar system simulations are developed by conduction, convection, and radiation relationship which describe the heat flow rate occurring in a building. In simulation some loads are more complicated to estimate than others. For instance, cooling load in passive solar system is more difficult loads to estimate compare to heating loads on both small (hourly) and large (annually) scale. The reason is “first, the difference between indoor and outdoor air temperature is typically smaller in cooling application so that the effect of solar radiation absorption on building surfaces is significant. Second, the ambient temperature may oscillate around the desired indoor temperature causing building thermal capacitance effects to be important. Third, the significant portion of the cooling load may result from the removal of water vapor from the air.”

In computer simulation it is really difficult to control the all parts of the design process and no matter how sophisticated a computer model becomes many limitation remains and they arise from the numbers of aspects. The mathematical imperfection that exits in the solution process, the difficulty of accurately modeling impacts and the rough calculation of complex modeling structure are some example of these limitation computers modeling in the building design process.

Design tool for building generally is classified as simulation or correlations. Simulations provide information on system performance over short (hourly) intervals of time. Correlations offer estimate of long term (monthly or annual). One of the best ways to establish a most excellent building design is to use simulation directly as a design tool. With a correct formulated simulation program and sufficient meteorological data every thing can be estimated and predicted. Simulation programs have a big variety in design field and they are available to community to use. However architect, engineers, designers and others who need to use the modeling program are more comfortable to use some programs that give them more options to play around during the design process, simpler to use, user friendly with more economical price.

Simulation programmers provide several suggestions to new designers to help them to accomplish a better design in the less period of the time. Planning a high-quality of process is as important as a planning a computer design. The model produced should be documented and maintained and be available to all designers to compare the result with each other and use the best available option. Superior contact with other designer is required because understanding and communication would develop across design group boundaries. Be cautious about each small detail which is involved in the design process since wrong number can lead the result to the wrong direction. The design should be carefully "partitioned" in the design process since it is easier to manage for later design groups. Even if it is possible for a small group of people to design and build out the entire project at the architectural level it is not possible at later levels of design.

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