While Harinder had it easy against South Africa's Gareth Naidoo, winning 11-7, 11-7, 11-5; Velavan pulled off a huge upset, beating No.1 seed Aqeel Rehman of Austria 11-3, 11-1, 11-5 in 31 minutes.
Having come through two qualifying rounds, Velavan, who won the British Junior Open earlier this year, looked in good touch and dismantled the top-seed without much fuss to set up a semifinal clash with No.3 seed Mark Fuller of England.
Earlier in the opening round, Velavan Senthilkumar had put it across eighth-seed Tiago Goriely (Belgium) 11-1, 11-5, 11-3.
Another Indian Guhan Senthilkumar had gone down to Aqeel Rehman 11-9, 11-1, 11-4 in the first round.