Development of three-dimensional visualisation technology of aerodynamic environment in fattening pig house using CFD and VR technology

Highlights

• Aerodynamic environment in a fattening pig house simulated using CFD.

• Three-dimensional image models were developed for inputting in a virtual space.

• A VR simulator was developed to visualise the aerodynamic environment in a fattening pig house.

Abstract

In this study, a virtual reality (VR) simulator to visualise the aerodynamic environment of a fattening pig house was developed as educational materials for farmers and consultants. The aerodynamic environments inside a fattening pig house were firstly analysed according to various environmental conditions using computational fluid dynamics (CFD). Using the validated CFD model (Kim et al., 2019), the aerodynamic environment inside the fattening pig house was analysed with 54 cases of environmental conditions in winter and 60 cases of environmental conditions in summer. And then, the VR simulator was developed by visualising the CFD-computed data of aerodynamic environments in virtual space. The three-dimensional fattening pig house models were designed following the CFD-computed cases, and the three-dimensional pig model was developed with real shape and texture. The virtual space was organized by arranging the three-dimensional image models of the fattening pig house and fattening pig. A C language-based code was also used to extract the CFD-computed results for developing visualisation of the aerodynamic environment inside the fattening pig house. Visualisation was realized using contour plot, two-dimensional vector flow, and smoke effect in the virtual space. In the case of the contour plot, a scalar of air temperature, relative humidity, and gas concentration were expressed using color on the active plane. A two-dimensional vector flow represented two-dimensional flows on the active plane. From streamline data, the smoke effect was developed to describe the airflow from the air inlet. In this study, a tablet-shaped user interface (UI) was created so that the user can directly select the desired cases. Through a performance test, the optimal number of frames was determined. Finally, the VR simulator was developed to effectively describe the aerodynamic environments inside the fattening pig house.

Introduction

Controlling the internal aerodynamic environment of the pig house is very important in South Korea due to the four distinct seasons. The optimum design of ventilation system is the most effective and economic method to maintain the optimal aerodynamic environment inside pig house. If the ventilation system is improperly designed inside the pig house, the air quality deteriorates with the poor environmental conditions of internal air temperature, humidity, gas concentration, etc. This poor environment can affect the pigs' behavior, weight gain, health, mortality, and physiological characteristics (Shi et al., 2006).

When the external cold air directly enters the pig house through the air inlet in winter, pigs may have cold stress (Song et al., 2004). This cold stress can cause swine flu and respiratory diseases. Because typical pig houses were generally operated with minimum ventilation in winter, the relative humidity and ammonia concentration in the pig houses increase resulting in a high risk of various disease occurrence. Further, because of the infiltration from the gap of old fans and doors, there is an air temperature fluctuation inside the pig room causing an increase of the heating cost. In summer, when the ventilation rate may be insufficient, the heat accumulates inside the pig house. Especially, the fattening pig is easy to suffer from high-temperature stress more than the weaning pig because the body temperature also increases as the weight of the pig increases (Pedersen and Sällvik, 2002). Kim (2015) reported that the body temperature of fattening pig may rises to more than 41 °C in summer. Thus, it may reduce the productivity of the pigs in summer due to high-temperature stress.

For the proper management of the environment in the pig house, proper ventilation is important. Because the inside airflow is the primary mechanism of transition and distribution of aerodynamic parameters such as air temperature, relative humidity, and gas concentration, it is necessary to properly control the aerodynamic environment inside the pig house through a proper ventilation system. Accordingly, the invisible aerodynamic environments inside pig houses should be accurately evaluated for making farmers and consultants understand the aerodynamic environments. However, farmers and consultant are hard to understand the internal airflow and environment distribution even if several sensors and analysis equipment for measuring the internal environment were installed at the pig farms. It lacks the tools for quantitatively evaluating and visualising the internal airflow and environment distribution.

One of the most effective methods for making farmers and consultants understand the aerodynamic environments is the field visiting which can see and check the actual environments of the pig house. However, there are limitations for quantitatively evaluating the internal airflow pattern although airflow pattern could be visualised by the use of smoke. Moreover, visiting pig farms is generally restricted due to the prevention of infectious diseases, especially in winter. For these reasons, an efficient alternative for the education on the internal ventilation system of the pig houses is necessary for a substitute for the field visiting. Many researches using computational fluid dynamics (CFD) have been conducted to qualitatively and quantitatively analyse aerodynamic environments of various ventilation systems in pig houses. Among them, many studies have been performed to analyse the thermal environment in pig houses using CFD simulation. Seo et al. (2012) created a three-dimensional pig model to represent the actual pig which was simplified in the CFD model. This study analysed the ventilation efficiency and thermal environment of a pig house in winter. Sousa Junior et al. (2018) analysed the distribution of thermal and wind environments according to the location of air inlets and outlets of the pig houses, and Li et al. (2016) compared the airflow and distribution of air temperature by designing pig models inside the pig house using CFD simulation. CFD simulation was also used for solving the problem of gas, dust, and odor generated in pig houses (Bjerg et al., 2011, Cruz et al., 2010, Kwon et al., 2016, Kwon et al., 2013, Zhang et al., 2009). Recently, the CFD-computed results conducted by the previous researches have been widely used for evaluating the ventilation system of the pig house. However, since the results using the conventional CFD technique in the previous studies have usually been represented by two-dimensional cross sections, these is the limitation for effectively expressing the internal aerodynamic environments in the pig houses for the non-expert to easily understand the ventilation system.

Recently, virtual reality (VR) technology has been greatly developed along with the fourth industrial revolution, creating opportunities for applying this technology in various fields such as medicine, education, and entertainment (Choi et al., 2010, Greenwald et al., 2017, Gunn et al., 2018, Kim et al., 2018, Shanahan, 2016). With the continuous development of computer graphics, it is now possible to make realistic three-dimensional image models. The realistic three-dimensional image models could be applied in the virtual space, providing a variety of realistic scenes. Accordingly, VR technology is one of the most suitable education materials to realistically visualise the aerodynamic environment inside the pig house (Kim et al., 2018). Though VR technology is widely used in many industries, there are only few attempts to apply it in the agricultural field. The educational VR simulators to visualise the aerodynamic environment in the greenhouse and piglet house have been developed (Kim et al., 2019, Kim et al., 2021a).

Therefore, the aim of this study was to develop a VR simulator to visualise the aerodynamic environment inside a fattening pig house as educational materials for farmers and consultants. The VR simulator, which is the software for experiencing the virtual space using VR devices, was developed by visualising the CFD-computed data of aerodynamic environments in virtual space. Especially, the VR simulator developed in this study was improved in the virtual space and visualisation technology compared to the previous VR simulator developed by Kim et al. (2019). For example, the three-dimensional fattening pig house and fattening pig models were improved by using the real shape and texture. Especially, the movements of fattening pigs in virtual space were realized for a more realistic effect. The visualisation of aerodynamic environment was improved by using contour plot, two-dimensional vector flow, and smoke effect in the virtual space. In addition, a tablet-shaped user interface (UI) was also created to effectively describe the aerodynamic environments inside the fattening pig house.