The aim of this study was to characterize the interaction between a pulsed ultrasonic wave and a paper forming screen for potential development of a smart paper forming sensor to measure velocity profile of the forming jet as it impinges on the wire. To achieve this goal, a Signal-Processing DOP 2000 pulsed ultrasonic Doppler velocimeter was used to generate a pulsed ultrasonic signal. The signal was transmitted and received using four different ultrasonic transducers: a 2 MHz 10 mm, 4 MHz 5 mm, 4MHz 8 mm focused, and 8 MHz 5 mm. The ultrasonic signals were then analyzed in order to determine the ultrasonic beam echo amplitude and shape. These tests were performed with and without various paper forming screens placed between the ultrasonic transducer and an ultrasonic signal target. Two different paper forming screens were utilized to study the interaction of the ultrasonic beam with the forming screens. The tests showed that the ultrasonic signal passing through the forming screens is greatly attenuated causing a sharp decrease in echo amplitude. To overcome the attenuation of the signal, a much higher amplification of the signal was used causing an increase in the saturation region around the forming screen. This increased the minimum distance that a target had to be away from the forming screen. The closest distance from the plastic sphere to the screen over the widest range of transducer-screen-distances that produced detectable echoes was achieved with the 4 MHz 5 mm transducer. The tests showed for both screens that there is more variation in beam width when the screen is moved laterally than when it is not moved at all. They also show that even though the pores in the forming screen are very small, they seem to have a great effect on the beam width measurements of the ultrasonic transducer.

The influence of turbulence on the orientation state of a dilute suspension of stiff fibers at high Reynolds number in a planar contraction is investigated. High speed imaging and LDV techniques are used to quantify fiber orientation distribution and turbulent characteristics. A nearly homogenous, isotropic grid generated turbulent flow is introduced at the contraction inlet. Flow Reynolds number and inlet turbulent characteristics are varied in order to determine their effects on orientation distribution. The orientation anisotropy is shown to be accurately modelled by a Fokker-Planck type equation. Results show that rotational diffusion is highly influenced by inlet turbulent characteristics and decays exponentially with convergence ratio. Furthermore, the effect of turbulent energy production in the contraction is shown to be negligible. Also, the results show that the flow Reynolds number has negligible effect on the development of orientation anisotropy, and the influence of turbulence on fiber rotation is negligible for $mathrm{Pe_r}>$ 10. It was concluded that inertia induced fiber motion played a negligible role in the experiments.