where assuming the returning probability (RP, [-]) to be the following equation for RP can be derived α, from equations (1) and (3): (4) where it is assumed that the component other that the amount of contaminant than α, is, (1−α) denotes that once transported out of the CV does not return to the CV (although it may still remain within the room) through recirculation, and this is defined as the [-] of the contaminant. NEP (5) In the above discussion, it is assumed that the returning probability is constant. This assumption is α considered rational based on the premise that the discussions are limited to a uniform flow field and the local domain is represented by a CV, the scale of which is the minimum scale of resolution in CFD. Moreover, introducing this assumption allows us to calculate the using the RANS model-based NEP CFD analysis. The concept described in this section is equivalent to the concept of visitation frequency, proposed NEP by the authors in a previous study, when applied to CV, and rearranged as probabilities7). The next section describes the relationship between and which is the velocity scale defining NEP NEV, the average velocity at the local “point.” 3. Relationship between and NEP NEV The authors have proposed two definitions of which is the vector quantity of the velocity scale NEV, that determines the average concentration of contaminant in the CV, using equations (6) and (7). The definitions are based on the assumption of a one-dimensional model (x-axis only) of the CV lattice structure8). Definition [1] (6)
where assuming the returning probability (RP, [-]) to be α, the following equation for RP can be derived from equations (1) and (3): (4) where it is assumed that the component other than α, that is, (1−α) denotes the amount of contaminant that once transported out of the CV does not return to the CV (although it may still remain within the room) through recirculation, and this is defined as the NEP [-] of the contaminant. (5) In the above discussion, it is assumed that the returning probability α is constant. This assumption is considered rational based on the premise that the discussions are limited to a uniform flow field and the local domain is represented by a CV, the scale of which is the minimum scale of resolution in CFD. Moreover, introducing this assumption allows us to calculate the NEP using the RANS model-based CFD analysis. The NEP concept described in this section is equivalent to the concept of visitation frequency, proposed by the authors in a previous study, when applied to CV, and rearranged as probabilities7). The next section describes the relationship between NEP and NEV, which is the velocity scale defining the average velocity at the local “point.” 3. Relationship between NEP and NEV The authors have proposed two definitions of NEV, which is the vector quantity of the velocity scale that determines the average concentration of contaminant in the CV, using equations (6) and (7). The definitions are based on the assumption of a one-dimensional model (x-axis only) of the CV lattice structure8). Definition [1] (6)