NASA grant funds aeroacoustic research to develop quieter vertical lift air vehicles

NASA has award­ed $5.7 mil­lion to a mul­ti-uni­ver­si­ty part­ner­ship as part of the agency’s Uni­ver­si­ty Lead­er­ship Ini­tia­tive.

The project, led by Boston Uni­ver­si­ty over the next three years, will bring togeth­er researchers and engi­neers from Vir­ginia Tech, Embry-Rid­dle Uni­ver­si­ty, Tuskegee Uni­ver­si­ty, and indus­try part­ner Joby Avi­a­tion to focus on devel­op­ing qui­eter ver­ti­cal lift air vehi­cles.

The grant will sup­port research into the tech­ni­cal and envi­ron­men­tal chal­lenges of fly­ing in urban envi­ron­ments. As pop­u­la­tions in urban areas con­tin­ue to grow, increased traf­fic and indus­tri­al activ­i­ty is caus­ing cities to become loud­er and loud­er. Fac­tor­ing in new modes of trans­porta­tion, such as ver­ti­cal lift air vehi­cles, will con­tribute to already exist­ing noise pol­lu­tion.

The research will devel­op meth­ods to bet­ter pre­dict low noise oper­a­tions of such vehi­cles with­in the urban canyon. The research team will explore how much the inges­tion of large-scale dis­tur­bances dur­ing flight, such as gusts of winds, will affect rotor noise.

“This is a com­pli­cat­ed prob­lem because while a heli­copter has one main rotor, these vehi­cles have mul­ti­ple rotors,” said Nathan Alexan­der, assis­tant pro­fes­sor in the Kevin Crofton Depart­ment of Aero­space and Ocean Engi­neer­ing.

“This pro­vides addi­tion­al degrees of free­dom to con­trol sound through indi­vid­ual rotor speed and tilt, but it also makes the prob­lem more com­plex. The goal is to deter­mine the opti­mal con­fig­u­ra­tion for safe oper­a­tions in unsteady envi­ron­ments that also pro­duce low noise.”

Both com­pu­ta­tion­al and exper­i­men­tal meth­ods will be used to sat­is­fy the research objec­tives. Vir­ginia Tech has been award­ed $1.3 mil­lion from the total NASA grant. Alexan­der, an expert in flu­id dynam­ics, flow-struc­ture inter­ac­tion, and flow gen­er­at­ed noise, will team with Nanya­porn Intaratep, research assis­tant pro­fes­sor, to plan and exe­cute test­ing in the Sta­bil­i­ty Wind Tun­nel.

The Sta­bil­i­ty Wind Tun­nel is one of the lead­ing uni­ver­si­ty-owned research facil­i­ties of its kind spe­cial­iz­ing in aero­dy­nam­ic and aeroa­coustic test­ing. In addi­tion to low back­ground noise, the facil­i­ty boasts state-of-the-art instru­men­ta­tion and capa­bil­i­ties for mea­sur­ing aeroa­coustic flow, such as its 251-chan­nel micro­phone array and stereo­scop­ic par­ti­cle image velocime­try sys­tems.

Work­ing with Joby Avi­a­tion, Alexan­der and Intaratep will design and con­duct exper­i­ments to assess the aero­dy­nam­ic and acoustic per­for­mances of mul­ti­ro­tor con­fig­u­ra­tions.

The team’s exper­i­ments will focus on the rotors them­selves – study­ing their inter­ac­tion in gusty envi­ron­ments, and mea­sur­ing the speed, thrust, torque, and noise from a vari­ety of angles, as well as the flow field in and around those rotors.

The data cap­tured will help val­i­date com­pu­ta­tion­al mod­els from uni­ver­si­ty part­ners to pre­dict the steady state noise as well as a vehicle’s response to dis­tur­bances in an urban set­ting. Through­out the exper­i­men­ta­tion phase, Alexan­der and Intaratep will also devel­op a vir­tu­al lab to increase the research’s edu­ca­tion­al impact.

“Most insti­tu­tions do not have a facil­i­ty like the Sta­bil­i­ty Wind Tun­nel,” Alexan­der added. “By using what we learned over the COVID-19 pan­dem­ic in deliv­er­ing a mean­ing­ful, online lab expe­ri­ence, we will be able to offer stu­dents at our part­ner uni­ver­si­ties the abil­i­ty to par­tic­i­pate in real flow and noise data acqui­si­tion and pro­cess­ing.”

The meth­ods and data derived from this study will be open-sourced, aid­ing in the indus­try advance­ment of ver­ti­cal lift air vehi­cles. The research will also pro­vide grad­u­ate and under­grad­u­ate stu­dents hands-on research expe­ri­ence relat­ed to the urban air mobil­i­ty indus­try.