Film Control to Study Contributions of Waves to Droplet Impact Dynamics on Thin Flowing Liquid Films

A protocol to study the contributions of waves to droplet impact dynamics on flowing liquid films is presented.

This method can assist us answer key questions in the fields of flowing liquid films, thin films, droplet impact.We digress to evolution dynamics of waves.They break up on the coalescence of droplets, and they also ingrain latches.So the main advantages of this technique is that it provides an avenue for us to study very thoroughly short timescale phenomena.To begin the procedure, clean the flat glass substrate with the soft cloth so that all dirt and particulate matter is removed from the surface of the substrate.Set the pivot of the substrate to the desired inclination angle.Fill the reservoir with the test liquid, such as deionized water.Start the fluid pump and confirm that the liquid flows normally across the entire substrate surface.Check the flow rate reading on the flowmeter, and gradually adjust the direct flow valve to attain the desired flow rate.Then, to avoid a hydraulic jump at the film inlet or a bad flow of air into the distribution chamber, adjust the knife end of the distribution chamber to set the gap height at the film head to the precise nuzzled film thickness value for the flowrate.Manually siphon the air from the distribution chamber to ensure a normal, uniform liquid flow across the entire substrate.Next, confirm that the function generator is connected to the solenoid valve in the liquid flow path through a non-latching relay.Then, turn on the function generator and the solenoid valve.Set the function generator to the desired forcing frequency and waveform.Then, fill up a syringe with the desired test liquid, such as deionized water.Connect clean plastic tubing into the syringe, and mount the syringe in the droplet generator assembly.Connect the needle of the desired diameter to the other end of the plastic tubing using paper tape.Mount the tubing and the syringe in the assembly.Adjust the needle position to achieve the desired fall height and streamwise impact point distance from the film inlet.Start the syringe pump and adjust the flow rate so that droplets of water are dripping from the needle onto the film without any detectable pre-acceleration.Continue adjusting the flowrate to achieve a droplet generation frequency that matches the wavelength of the waves on the surface of the film, which ensures that droplets will fall on different regions of the film.Place light diffusers in front of the light sources, and turn on the light.Confirm that the imaging area is uniformly illuminated, and then turn off the light.Next, switch off the function generator and droplet generator.Mount a high-speed camera on a tripod.Fit the camera with a macrolens that has the desired focal length and turn on the camera.Focus the camera on the film surface with a 7