This work deals with the performance analysis of supersonic ejectors. A CFD model to predict the ejector performance in terms of suction and entrainment capacities is presented and applied to different operation modes of an air ejector.Computational results are compared to pressure and mass flow rate measurements. The 2D axisymmetric CFD model proves its ability to correctly predict the optimum operating conditions for supersonic ejectors.

Background: Orthodontic retainers constrict the oral cavity's dimension and restrict tongue movement during articulation, resulting in distortions of various sounds. Speech impairment is among the main reason for poor patient compliance in wearing the retainers which leads to treatment relapse. Objectives:To determine and describe the changes of the distorted sounds in patients wearing upper and lower Hawley retainer. Materials and methods:Sixteen orthodontic patients who were at the end of fixed appliance phase were included as subjects in this study. They were all speakers of native Malay, aged between 15 to 31 years old. The sound sample of selected phonemes with /t/, /d/, /k/ and /n/ consonant were recorded from the subjects before wearing (T 0 ), immediately after wearing retainers (T 1 ), and at 1 week (T 2 ), 2 weeks (T 3 ), 1 month (T 4 ), 2 months (T 5 ) and 3 months (T 6 ) of wearing the retainers. Based on the recordings, acoustic analysis was performed objectively on each subject to determine the duration value of selected phonemes at each interval.Results: All phonemes tested showed significant speech distortion (p<0.008) immediately after wearing the retainers. After one week, /k/ sound showed marked improvement in all subjects. Significant distortion of /n/ sound was recorded (p<0.008) for up to 2 months. No significant speech distortions were recorded after 3 months (p>0.008). Conclusions:A marked distortion of /t/, /d/, /k/ and /n/ consonant sounds were observed in patients during the initial wearing of Hawley retainer. Patient needs to be well informed of the changes and encouraged for constant wearing. With good cooperation, speech will be adapted to normal pattern within 3 months.

The measurement of the static pressure of the flow inside a supersonic ejector can be achieved by using a thin tube with a radially drilled hole to capture the flow pressure, and which is inserted along the ejector axis. This paper presents a numerical study by CFD permitting to predict the disturbances generated by the presence of the probe in the ejector. Also this study allows guiding the design of the probe, in particular of the capillary tube diameter for the least disturbed measurement. A probe prototype has been built and tested on an ejector test bench.

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