Modelling the effect of an occupant on displacement ventilation with computational fluid dynamics

International audienceDisplacement ventilation of a room with an occupant is modelled using computational fluid dynamics (CFD) and compared against experimental data. The geometry of the experimental manikin is accurately represented in the CFD model to minimise potential errors from using a simplified form. Modelling thermal radiation from the manikin is found to be important and calculations using a radiation model show good agreement with experimental data. The influence of turbulence modelling is considered and a comparative study is made between an unsteady Reynolds-averaged approach (URANS) and detached-eddy simulation (DES). The results show that the URANS and DES give similar predictions with the DES results in slightly better agreement with the experimental data. The realistic manikin geometry is required to give accurate heat transfer and contaminant exposure predictions; such geometries can be handled with relative ease using current grid generation tools and CFD solvers

A comparison of a range of models for dispersion in a partially stratified room

International audienceA comparative study of models used to predict contaminant dispersion in a partially stratified room is presented. The experiments were carried out in a ventilated test room, with an initially evenly dispersed pollutant. Air was extracted from the outlet in the ceiling of the room at 1 and 3 air changes per hour. A small temperature difference between the top and bottom of the room causes very low air velocities, and higher concentrations, in the lower half of the room. Grid-independent CFD calculations were compared with predictions from a zonal model and from CFD using a very coarse grid. All the calculations show broadly similar contaminant concentration decay rates for the three locations monitored in the experiments, with the zonal model performing surprisingly well. For the lower air change rate, the models predict a less well mixed contaminant distribution than the experimental measurements suggest. With run times of less than a few minutes, the zonal model is around two orders of magnitude faster than coarse-grid CFD and could therefore be used more easily in parametric studies and sensitivity analyses. For a more detailed picture of internal dispersion, a CFD study using coarse and standard grids may be more appropriate

Extra-linguistic influences on sentence comprehension in Italian-speaking children with and without specific language impairment.

BACKGROUND: Many children with specific language impairment (SLI) have deficits in sentence comprehension. These deficits are usually attributed to limitations in the children’s understanding of syntax or the lexical items contained in the sentences. In this study, we examine the role that extra-linguistic factors can play in these children’s sentence comprehension. AIMS: In this study, extra-linguistic demands on sentence comprehension were manipulated directly by varying the nature of the materials used. METHODS & PROCEDURE: Forty-five Italian-speaking children participated: 15 with SLI (M age = 4;5), 15 typically developing children matched for age (TD-A, M age = 4;5), and 15 younger typically developing children matched according to language comprehension test scores (TD-Y, M age = 3;9). The children responded to sentence comprehension items that varied in their length and/or in the number and type of foils that competed with the target picture. OUTCOME & RESULTS: The TD-A children were more accurate than the TD-Y children and the children with SLI, but, for all groups, accuracy declined when task demands increased. In particular, sentences containing superfluous adjectives (e.g., Il topo bello copre l’uccello allegro “The nice mouse covers the happy bird” where all depicted mice were nice and all birds were happy) yielded higher scores than similar sentences in which each adjective had to be associated with the proper character (e.g., Il cane giallo lava il maiale bianco “The yellow dog washes the white pig” where foils included a yellow dog washing a pink pig, and a brown dog washing a white pig). Many errors reflected recency effects, probably influenced by the fact that adjectives modifying the object appear at the end of the sentence in Italian. CONCLUSIONS & IMPLICATIONS: Differences between conditions were observed even when lexical content, syntactic structure, and sentence length were controlled. This finding suggests the need for great care when assessing children’s comprehension of sentences. The same syntactic structure and lexical content can vary in difficulty depending on the number and types of foils that are used in combination with the target picture

Clinical markers for specific language impairment in Italian: the contribution of clitics and non-word repetition

none6The discovery of clinical markers for specific language impairment (SLI) in children can assist in the accurate identification of children with this disorder, and in a description of the disorder’s phenotype for genetic study. One challenge to this type of research is the fact that languages vary in the most salient symptoms of SLI. This study focuses on Italian. Aims: To determine whether three measures — the use of third-person plural inflections, the use of direct-object clitics and non-word repetition — are successful in distinguishing Italian-speaking children with SLI from their typically developing peers. Methods & Procedures: Eleven preschool-aged children with SLI, 11 same-age typically developing peers and 11 younger typically developing children participated in the study. The third-person plural inflection and direct-object clitic tasks required the children to describe drawings in response to prompts provided by the examiner. In the non-word repetition task, the children repeated non-words ranging from one to four syllables in length. Outcomes & Results: All three measures proved successful either singly or in combination, with direct-object clitics and non-word repetition showing the highest sensitivity and specificity. Conclusions: Additional research should be pursued to replicate and extend these findings. Along with the potential clinical value of the findings, the results suggest that difficulties with non-final weak syllables — a problem that would adversely affect all three measures — may be an important part of the SLI profile in Italian.mixedBORTOLINI U; B. ARFE'; CASELLI M.C; DE GASPERI L; DEEVY P; LEONARD LBortolini, U; Arfe', Barbara; CASELLI M., C; DE GASPERI, L; Deevy, P; Leonard, L