The former hooker will replace Chris Gibbes, who confirmed in January he will become head coach of the Wellington Lions in New Zealand.
Capped eight times by Ireland, Clarke was a part of the Ulster team which won the 1999 Heineken Cup.
"I'm delighted to have this opportunity and really excited about the next challenge in my career," said Clarke.
As a coach, the 49-year-old helped the province win the 2006 Celtic League title before joining the Irish Rugby Union as high performance manager.
He returned to Ulster in 2012 and became forwards coach two years later.
Clarke also has international coaching experience with Ireland A and Emerging Ireland, with whom he won the 2015 Tbilisi Cup ahead of Georgia, Italy A and Uruguay.
"I'm looking forward to the challenge," added Clarke.
"It's an ambitious organisation with a great mix of experience and some real talent coming through and I hope I can add value for the players, the coaches and the management.
"Chris Gibbes has done a great job in building a pack that has the potential to go toe-to-toe with anyone and I'm grateful to have that platform to work from when I arrive in the summer."

The Phoenix Tent will also host New York indie pop outfit The Pains of Being Pure at Heart.
Joining them will be SLUG, a new band fronted by former Field Music bassist Ian Black and collaborative duo Aidan Moffat and Bill Wells.
The festival near Dundrennan takes place on 24 and 25 July.
The Wickerman Festival's Brian Reynolds said: '"With just five weeks to go until this year's festival, it's fantastic to announce our new stage and the raft of talent that it will showcase.
"We are confident that the mix of acts will be a big hit with Wicker fans."

The sum is on top of more than £1.2bn set aside in previous years' provisions.
Parent company National Australian Bank (NAB) said between £350m and £500m more would be set aside this year, but added that the final cost remained uncertain.
The move was announced in its third quarter results on Monday.
Up until the end of March, NAB had set aside £806m to compensate customers for the mis-selling of payment protection insurance (PPI). A total of £325m has already been paid out.
NAB's cumulative provisions relating to interest rate hedging products amounted to £431m, about half of which has been paid out.
This year's extra funding will come from a £1.7bn mis-selling fund, which the bank is being required by UK regulators to make available after the Clydesdale is floated.
NAB is in the process of demerging and floating Glasgow-based Clydesdale, which includes the Yorkshire Bank.
It intends to complete the break-up by the end of this year.
In a statement, NAB said "substantial progress" had been made on the demerger and stock market sale. It will provide more detail with full-year results in late October.
The Australian banking group has been working hard to offload the Clydesdale, which amassed a large portfolio of bad property loans.
It has also been facing high costs of redress for mis-selling payment protection insurance and complex systems for business customers to protect against interest rate changes.
Ulster forwards coach Allen Clarke will join Ospreys at the end of the season.
[NEXT_CONCEPT]
Scottish band the BMX Bandits have been announced as one of the acts playing a new contemporary music stage at the Wickerman Festival.
[NEXT_CONCEPT]
Clydesdale Bank is to set aside as much as £500m in extra funding this year to compensate customers for mis-selling of financial products.